Self Eval for Cells and Genetics

REGARDING YOUR OWN PERFORMANCE

1. What were the three aspects of the assignments I've submitted that I am most proud of?

I am proud of my cell model in total. I am not very creative in an artistic and I think it turned out fairly well. The other aspects of my cell regarding mitosis and what not were not bad either, again, because I am not very good at that type of work

2. What two aspects of my submitted assignments do I believe could have used some improvement?

I did the best I could with my work but I suppose with better time management I could have improved everything.

3. What do I believe my overall grade should be for this unit?

An A because I am anal-retentive and I can only handle 1 B a semester and since I am taking a math class (which I suck at) it should be there and not here.

4. How could I perform better in the next unit?

BETTER TIME MANAGEMENT!!!!

1. At what moment during this unit did you feel most engaged with the course?

   Making my cell helped a lot, but it is hard to be disengaged from a course completing a compendium review.

2. At what moment unit did you feel most distanced from the course?

   Trying to do all my other homework.

3. What action that anyone (teacher or student) took during this unit that find most affirming and helpful?

   All my e-mails and questions were answered and I felt comfortable that the behavior would continue.

4. What action that anyone (teacher or student) took during this unit did you find most puzzling or confusing?

   N/A

5. What about this unit surprised you the most? (This could be something about your own reactions to the course, something that someone did, or anything else that occurs to you.)

I found this subject more fascinating than I thought and I am thinking a switching to a applied science major instead of applied arts.

Human cloning-Want or Waste?

Cloning has been an issue at the forefront of genetic technology for quite sometime. There are both advantages and disadvantages to cloning. The issues of cloning encompass not only the scientific community, but also religion and morality.

Human cloning is the creation of a genetically identical copy of a human being, human cell, or human tissue. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning part of the natural process of reproduction.

There are different types of cloning that each entail different results. Reproductive cloning is a technology used to generate an animal that has the same nuclear DNA as another currently or previously existing animal. Therapeutic cloning, also called "embryo cloning," is the production of human embryos for use in research. The goal of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease.

Reproductive cloning is expensive and highly inefficient. More than 90% of cloning attempts fail to produce viable offspring. More than 100 nuclear transfer procedures could be required to produce one viable clone. In addition to low success rates, cloned animals tend to have more compromised immune function and higher rates of infection, tumor growth, and other disorders.

Physicians from the American Medical Association and scientists with the American Association for the Advancement of Science have issued formal public statements advising against human reproductive cloning. Currently, the U.S. Congress is considering the passage of legislation that could ban human cloning. Many other countries may adopt that legislation too.

Another concern of human reproductive cloning and genetic engineering, is the factor that parents may want to customize their children. Many religious organizations are up in arms against this, citing the word of God as a shield for natural reproduction.

Greenpeace believes that genetically modified organisms (GMO) can spread through nature and interbreed with natural organisms, thereby contaminating non-genetically engineered environments and future generations in an unforeseeable and uncontrollable way. The release is 'genetic pollution' and is a major threat because GMOs cannot be recalled once released into the environment.

On the other hand, stem cells are important to biomedical researchers because they can be used to generate virtually any type of specialized cell in the human body. Stem cells are extracted from the egg after it has divided for 5 days. The extraction process destroys the embryo, which raises a variety of ethical concerns.

However, researchers hope that someday stem cells can be used to serve as replacement cells to treat heart disease, Alzheimer's, cancer, and other diseases. Human therapeutic cloning could provide genetically identical cells for regenerative medicine, and tissues and organs for
transplantation. Such cells, tissues, and organs would neither trigger an immune response nor require the use of immunosuppressive drugs.

Human reproductive cloning may also have benefits. Researchers and doctors hope to create a fertility treatment that allows parents who are both infertile to have children with at least some of their DNA in their offspring. Reproductive cloning also could be used to repopulate endangered animals or animals that are difficult to breed.

This is an issue that does not have any solution that will appease everyone involved. Families with sick children may want their child to be healthy, no matter what the cost; financial, moral, or otherwise. Scientists want to continue their work unabated and unrestrained by the religious and moral conservatives and the interference of the government.

Dragon Genetic and the Punnett Square

Dragon Genetics and the Punnett Square


dragon genetics showing how the manipulation of alleles changed the dragon phenotype


Punnett square showing the traits of the fruitfly


Genetics is the study of biological inheritance. The molecular basis for our genes is DNA. DNA is composed of a chain of nucleotides and our genetic information exists along the chain. Chromosomes are the genes arranged along the DNA chain.

genotype- the genes of an individual
phenotype-trait or characteristic affected by the genotype
allele-alternative forms of a gene having different locus on the same chromosome, occur in pairs
cross-A monohybrid cross is a genetic cross where only one gene/trait is being studied. A dihybrid cross is a cross where two traits/genes are under consideration.
dominant (allele)-the one that’s fully expressed; symbolized by a capital letter, often the first letter of the word for which it stands
recessive (allele)-the one that’s almost always completely masked; symbolized by the SAME letter, but lower case. If a person has 2 recessive genes, that phenotype is expressed.

During gametogenesis, the chromosome number is reduced. A chromosome has 46, a gamete 23. This occurs as a result of meiosis. A monohybrid is an individual that is heterozygous to one pair of alleles. The Punnett sqaure is a tool which helps determine the outcome of genotypes/phenotypes. The genotypic ratio is 1:2:1 and the phenotypic ratio 1:3:1.

Genetic inheritance is influenced by the arrangement of alleles during fertilization. During meiosis (reduction division) , each of the parent cells contribute 1/2 of their chromosomes utilized during fertilization. Dependent upon the genotypes of both parents, the offspring will have different but predictable chances of inheriting certain traits. The Punnett square is a diagram which simplifies the process of determining the percentages of inheriting certain traits.

The gametes carry genes that are dominant or recessive. Upon fertilization, the combination of the genotypes determines the phenotype of the offspring.

Alleles occur in pairs and normally an individual has 2 alleles for each trait. A person with 2 dominant alleles has a homozygous dominant genotype. A person with 2 recessive alleles has a homozygous recessive genotype. A person with one of each has a heterozygous genotype. The genotype refers to the genes, the phenotype to the trait or characteristic.

Genetic inheritance is important for myriad reasons, but especially for the study and ramifications of many genetic diseases and disorders. Genetic disorders can be autosomal dominant: an individual with the alleles AA or Aa will have the disorder, or autosomal recessive: an individual with the alleles aa will have the disorder. A person's genome can be modified. Gene therapies such as ex vivo gene therapy or in vivo gene therapy can treat different medical conditions.

Genetic material must be able to do 3 things: replicate so it can be transmitted to the next generation, store information, and undergo mutations that provide genetic variability.

Online Lab Activity

onion cell at 40x magnification

Microscopy is the technical field of using microscopes to view samples or objects. The development of microscopes opened the field of science to a whole new dimension. Scientists discovered microorganisms, cellular structure, and the smallest parts of plants and animals on the planet, and more importantly, viruses. Dating as far back as 2600 b.c., rock crystal artifacts found in the shape of convex lenses were found. Over time, the progression for the use of lenses in scientific work continued until the late 1500's.

Zacharias and Hans Janssen are credited with the production of the first microscope around 1595. The first compound microscope had a 3x-9x magnification. Robert Hooke continued research on the initial premise and improved the compound microscope around1660. Anton Leeuwenhoek built a simple one lens microscope in during the late 1600's and early 1700's. They were reportedly the best in his time. In 1873, Ernst Leitz developed a microscope with a revolving nose piece for objectives. Max Knoll and Ernst Ruska built the first electron microscope in 1931 and 2 years later Ruska increased the magnification of the electron microscope to higher levels than the complound light microscope.

There are different types of microscopes: compound-light, dissection, scanning electron microscope (SEM), and transmission electron microscope (TES.) The compound light microscopes are light illuminated. The image seen with this type of microscope is two dimensional. This microscope is the most commonly used. You can view individual cells, even living ones. It has high magnification. However, it has a low resolution. A dissection microscope is light illuminated. The image that appears is three dimensional. It is used for dissection to get a better look at the larger specimen. You cannot see individual cells because it has a low magnification. SEM use electron illumination. The image is seen in 3-D. It has high magnification and high resolution. The specimen is coated in gold and the electrons bounce off to give you and exterior view of the specimen. The pictures are in black and white. TEM is electron illuminated. This gives a 2-D view. Thin slices of specimen are obtained. The electron beams pass through this. It has high magnification and high resolution.



fig.cox.miami.edu/.../light.microscope.gif


The parts of a microscope:

• Eyepiece
• Objectives
• Fine Adjustment Knob
• Power Switch
• Stage
• Diaphragm
• Base
• Body Tube
• Nosepiece
• Stage Clips
• Stage Stop
• Coarse Adjustment Knob
• Aperture
• Arm
• Light Source

To utilize a microscope you must first turn on the light and adjust the rheostat. The stage of the microscope is the area of the microscope where the slide is placed utilizing stage clips to hold the slide securely. The ocular housing is turned to select the magnification lens. The specimen is centered over the iris and the course adjustment knob is used to set the stage as high as it will go. You must adjust the oculars of the microscope while looking through them to view your specimen. The course focus knob is used while looking through the microscope on low power with the stage at the top until the image appears. The fine focus knob is used to clarify the image and the iris diaphragm to adjust the light. The objective lenses have different magnifications and the and the focus and iris diaphragm must be adjusted to compensate for the different magnifications. If the focus knobs and iris diaphragm are not utilized properly, the image quality will be poor, if the image is visible at all.

Cell Model

Animal Cell Model

This is the model of an animal cell utilizing various beads, gems, ribbons, thread and other craft items. I constructed the cell, along with an example of DNA, RNA, the process of mitosis, and the process of transcription and translation. The project began as this:


The beginning...

and continues...

My cell consists of the following:

• Cell - large white styrofoam disc
  
• Cell membrane- dark purple ribbon
• Ribosomes- small pink gems
• Lysosomes- dark purple gems
• Vesicles- light purple gems
• Endoplasmic Reticulum- folded purple ribbon
• Golgi Apparatus- folded light purple ribbon
• Mitochondria- striated pink glass beads
• Centrosome- red star
• Microtubules (cilia, flagella)- toothpicks
• Nucleus- small white styrofoam disc
• Nuclear membrane-compiled dark purple ribbon with light purple dotted overlay (for nuclear pores)
• Nucleolus- black button
  
• Chromatin- purple thread
• Chromosomes- purple and blue pipe cleaners

Prior to completing the cell model, I constructed the following pictures to represent the following, as I could not fit them into my completed cell model:

DNA Ladder Structure

Although normally a double helix, the above picture represents DNA in ladder structure:

• White buttons- phosphates
• Pink gems- deoxyribose sugar
• Blue gems- thymine
• Yellow gems- adenine
• Red Gems- cytosine
• Green gems- guanine

Notice that the strands are antiparallel.

Structure of RNA

The above picture represents RNA:

• White buttons- phosphate
• Pink gems- ribose
• Green gems- guanine
• Purple gems- uracil (instead of thymine in DNA)
• Yellow gems- adenine
• Red gems- cytosine

The following pictures represent transcription and translation:


Transcription

Transcription occurs within the nucleus. The DNA molecule serves as a template for RNA. The mRNA is processed prior to leaving the nucleus. The mRNA leaves the nucleus a mature mRNA through the disintegrating nuclear membrane.

• Green pipe cleaner -DNA
• Purple pipe cleaner- mRNA
• Green gems- guanine
• Red gems- cytosine
• Yellow gems- adenine
• Purple gems- uracil
• Blue gems- thymine
• White area- nucleus
  

Translation occurs outside the nucleus:

mRNA moving into cytoplasm to ribosomes

• White button- nuclear pore
• Purple pipe cleaner- mRNA
• Coconut doughnut- small and large ribosomal subunits

tRNA

• Oblong green gems- tRNA
• Red-Yellow-Purple gem chain- anticodon
• Blue gem/yellow gem- peptides
  

tRNAs with anticodons carry amino acids to mRNA. Inside the ribosomal subunits, the anticodon-codon base pairing occurs and the polypeptide synthesis takes place one amino acid at a time.

Translation

• White area- cytoplasm
• Coconut doughnut- ribosome
• Large purple beads strung together- peptides
• Purple pipe cleaner- mRNA
• Oblong green gems- tRNA
• Bottom row of gems along purple pipe cleaner grouped in 3's- codons
• Group of gems by 3's near the green oblong gem- anticodons
  

Mitosis is duplication division. The following pictures represent mitosis:

• Purple and blue pipe cleaners-chromosomes/sister chromatids
  
• Purple thread- Chromatin
• Brown thread- spindle fibers
• Pink gems- spindle poles

Early prophase-centrosomes have duplicated, chromatin is condensing


Prophase- nucleolus has disappeared and duplicated chromosomes are visible, spindle in the process of forming


Early metaphase- each chromatid is attached to a spindle fiber, spindle fibers stretch from each pole and overlap


Metaphase-centromeres of duplicated chromosomes are aligned at the equator, spindle fibers are attached to the sister chromatids come from opposite spindle poles


Anaphase-sister chromatids part and become daughter chromosomes that move toward spindle poles (obviously the cells would still be pulling apart and not separate yet)


Telophase-daughter cells are forming as nuclear envelopes and nucleoli reappear


The final product...


Animal cell completion with key




Completed cell

• Cell - large white styrofoam disc
  
• Cell membrane- dark purple ribbon
• Ribosomes- small pink gems
• Lysosomes- dark purple gems
• Vesicles- light purple gems
• Endoplasmic Reticulum- folded purple ribbon
• Golgi Apparatus- folded light purple ribbon
• Mitochondria- striated pink glass beads
• Centrosome- red star
• Microtubules (cilia, flagella)- toothpicks
• Nucleus- small white styrofoam disc
• Nuclear membrane-compiled dark purple ribbon with light purple dotted overlay (for nuclear pores)
• Nucleolus- black button
  
• Chromatin- purple thread
• Chromosomes- purple and blue pipe cleaners

View of cell showing cell membrane and nuclear membrane

Compendium Review-Cells and Genetics 2

Table of Contents

Patterns of Chromosome Inheritance
Cancer
Patterns of Genetic Inheritance
DNA Biology and Technology


Patterns of Chromosome Inheritance

Humans have 46 chromosomes that occur in 23 pairs. 22 of the pairs are called autosomes, one pair is the sex chromosome. Males have the XY chromosome and females the XX. Chromosomes are visible in all cells of the body barring red blood cells. A computer display of the chromosomes is called a karyotype.

cancergenome.nih.gov/media/karyotype_black_im...

Mitosis (duplication division) is the process that insures every cell has 46 chromosomes. In dividing cells each chromosome is composed of 2 identical parts called sister chromatids. Chromatids are held together at the region called the centromere. The centromere holds the two together until the phase of mitosis where the centromere splits.

http://nobelprize.org/nobel_prizes/medicine/laureates/2001/eng.gif

The cell cycle is an orderly process composed of 2 parts: interphase and cell division. Most of the cell cycle is spent in interphase. During this time, organelles carry on their usual function. The cell also gets ready to divide and as it grows larger, the number of organelles doubles as does the amount of chromatin and DNA synthesis occurs. DNA synthesis permits interphase to be divided into 3 stages: G1, S, and G2.

• G1- A cell doubles its organelles and accumulates the material needed for DNA synthesis
• S- DNA replication occurs, resulting in duplicated chromosomes
• G2- The cell synthesizes proteins needed for cell division
  

Following interphase, cell division occurs. Cell division has 2 stages: M (miotic) and cytokinesis. Mitosis is a type of nuclear division. Cytokinesis is the division of cytoplasm.

• M- the sister chromatids separate becoming chromosomes w/2 daughter nuclei
• Cytokinesis- 2 daughter cells present

The cell cycle occurs continuously in certain tissue. Apoptosis (programmed cell death) occurs to do away with cells that are dividing when they should not.

Mitosis is duplication division. The dividing cell is the parent cell, the new cells are called the daughter cells. They are genetically identical. During mitosis, chromatin in the nucleus becomes highly condensed and the chromosomes become visible. The sister chromatids are held together by the centromere. After the centromeres split, the sister chromatids separate.

www.houghtonmifflinbooks.com/.../mitosis1.gif

An important event of mitosis is the duplication of the centrosome, the microtubule organizing the center of the cell. After they separate, the form the poles of the miotic spindle, where the centrosomes assemble the microtubules that make up the spindle fibers. The chromosomes are attached to the fibers by the centromere. An array of microtubules is called an aster. Centrioles are short cylinders of microtubules present in centrosomes.

There are four phases of mitosis: prophase, metaphase, anaphase, and telophase. Although they appear as four separate stages, they are one continous, fluid phase without interruption.

• Prophase- centrosomes have duplicated and the nucleolus has disappeared, duplicated chromosomes are visible

img.sparknotes.com/.../prophase.gif

• Metaphase- each chromatid is attaced to a spindle fiber, cetromeres of the duplicated chromosomes are aligned with equator

img.sparknotes.com/.../metaphase.gif

• Anaphase- sister chromatids part and become daughter chromosomes that move toward spindle poles

img.sparknotes.com/.../anaphase.gif

• Telophase- daughter cells are forming as nuclear envelopes and nucleoli reappear

img.sparknotes.com/.../telophase.gif

Cytokinesis is the division of the cytoplasm and organelles. In human cells, a slight indentation, the cleavage furrow, passes around the circumference of the cell. Actin filaments form a contractile ring and the cleavage furrow pinches the cell in half. Each cell becomes enclosed by its own plasma membrane.

img.sparknotes.com/.../cytokinesis.gif

Meiosis is reduction division. Because meiosis involves two divisions, there are 4 daughter cells. Each daughter cell has 1 of each kind of chromosome, therefore half as many as the parent cell. The parent cell is diploid (2n) and the daughter cell haploid (n.) Daughter cells which result from meiosis are gametes.

At the start of meiosis there are 2 chromosome pairs which are homologues. The 2 cell divisions of meiosis are broken into meiosis I and meiosis II. Prior to meiosis I, DNA replication has occurred. During meiosis I, The homologous chromosomes line up side by side, called synapsis. The period between meiosis I and II is called interkinesis.

• Meiosis I- duplicated homologous pairs synapse and separate

kvhs.nbed.nb.ca/gallant/biology/meiosis_1.jpg

• Meiosis II- sister chromatids separate becoming daughter chromosomes

kvhs.nbed.nb.ca/gallant/biology/meiosis_2.jpg

In humans, daughter cells mature into gametes or sex cells that fuse during fertilization. Fertilization restores the haploid number to a diploid number in the zygote, the first cell of a new individual. Meiosis I and II are broken down into four stages each meiosis I stages with a I and meiosis II stages with a II. Here we discuss meiosis I stages:

• Prophase I- synapsis and crossing over occur
• Metaphase I- homologous pairs align independently at equator
• Anaphase I- homologous chromosomes separate and move toward poles
• Telophase I- daughter cells are forming and will divide again

www.accessexcellence.org/.../images/meiosis.gif

Meiosis is a part of spermatogenesis, the production of sperm in males and oogenesis, the production of eggs in females.

fig.cox.miami.edu/~cmallery/150/devel/sf45x3.jpg

An individual may be born with too few or too many autosomes or sex chromosomes. This is usually due to nondisjunction during meiosis. If nondisjunction occurs, a person could have trisomy, one type of chromosome present in 3 copies, or monosomy, one type of chromosome is present in a single copy. The most common autosomal trisomy is Down Syndrome, or trisomy 21.

anthro.palomar.edu/.../images/karyotype_Down.gif

Changes in the number of sex chromosomes also result in various sydromes. With Turner Syndrome, an individual has only one sex chromsome, an X. In Klinefelter Sydrome, a male has 2 X chromosomes and 1 Y chromosome. Some females have more than 2 X chromosomes and extra Barr bodies in the nucleus. They are referred to as Poly-X females. Jacobs Syndrome results from a chromosome pattern of XYY.

Changes in chromosome structure are another type of chromosomal mutation.

• Deletion- occurs when an end of a chromosome breaks off or when 2 simultaneous breaks lead to the loss of an internal segment
• Duplication- the presence of a chromosomal segment more than once n the same chromosome
• Inversion- a segment of the chromosome is turned around 180 degrees
  
• Translocation- a movement in the chromosome segment from one chromosome to antother nonhomologous chromosome

Cancer

Cancer encompasses over a hundred different diseases, although differing in type, they have common characteristics.

• Lack differentiation
  
• Have abnormal nuclei and fail to undergo apoptosis
• Have unlimited replicative potential due to telomerase
• Form tumors
• No need for growth factors and do not respond to inhibitory growth factors
• Gradually become abnormal through a multistage process of initiation, promotion and progression
• Undergo angiogenesis ( the formation of new blood vessels) and metastasis (cells that begin new tumors far from the primary tumor)
  

cache.eb.com/eb/image?id=66377&rendTypeId=4

Cancer is a genetic disease due to mutations on two types of genes: the proto-oncogenes and the tumor-supressing genes. When a proto-oncogenes mutate they become cancer-causing oncogenes. Whatever a proto-oncogene does an oncogene does better. When tumor-supressor genes mutate, they no longer inhibit the cell cycle and promote apoptosis.

www.healthofchildren.com/images/gech_0001_000...

Oncology is the study of cancer. Tumors are classified to their place of origin. Carcinomas are cancers of the epithelial tissues and adenocarcinomas are cancers of the glandular epithelial cells. Sarcomas are cancers of muscle, bone, and connective tissues. Leukemias are cancers of the blood and lymphomas cancers of the lymphatic tissue. Patterns of cancer development have shown that there are genetic and environmental risk factors for cancers as well as some guidelines that may prevent cancer:

Causes of cancer:

• Hereditary
• Mutagens- an agent which causes mutation
• Carcinogens- a chemical which causes cancer
• Radiation- UV light, radon gas, nuclear fuel/waste, X-rays
• Organic chemicals- tobacco smoke, pollutants
• Viruses- Hep B & C, Epstein-Barr virus, HPV
• Dietary choices- avoid nitrite cure food, avoid obesity and high fat foods
  

Prevention behaviors:

• Don't smoke or chew
  
• Don't sunbathe
• Avoid alcohol
• Avoid radiation
• Get tested for cancer
• Avoid exposure to occupational hazards
• Awareness of hormone replacement therapy
• Vaccines
• Diet which consists of high fiber foods, antioxidents, vegetables

The earlier cancer is detected, the greater chance of effective treatment. Seven warning signs for cancer: Change in bowel or bladder habits, A sore that does not heal, Unusual bleeding or discharge, Thickening or lump in breast or elsewhere, Indigestion or difficulty swallowing, Obvious change in wart or mole, Nagging cough or hoarseness. CAUTION

There are routine screening tests for cancer and self examination, along with regular check ups and blood work from a doctor, prove invaluable. Genetic testing is also available.

The treatment of cancer has evolved, but there are standard therapies in use:

• Surgery
• Radiation
  
• Chemotherapy, sometimes in conjunction with bone marrow transplants

Newer treatments involve immunotherapy, p53 gene therapy, and possibly drugs that inhibit angiogenesis.


Pattern of Genetic Inheritance

A genotype refers to the genes of an individual. Alternative forms of a gene having a different locus on a pair of chromosomes and affecting the same trait are alleles. It is customary to designate an allele by a letter which represents a specific trait. A dominant allele is assigned uppercase and a recessive allele lowercase. Alleles occur in pairs and normally an individual has 2 alleles for each trait. A person with 2 dominant alleles has a homozygous dominant genotype. A person with 2 recessive alleles has a homozygous recessive recessive genotype. A person with one of each has a heterozygous genotype. The genotype refers to the genes, the phenotype to the trait or characteristic.

ghs.gresham.k12.or.us/.../pics/alleles.gif

During gametogenesis, the chromosome number is reduced. A chromosome has 46, a gamete 23. This occurs as a result of meiosis. A monohybrid is an individual that is heterozygous to one pair of alleles. The Punnett sqaure is a tool which helps determine the outcome of genotypes/phenotypes. The genotypic ratio is 1:2:1 and the phenotypic ratio 1:3:1.

trc.ucdavis.edu/.../bis10v/week4/punnett.gif

Two trait crosses are a bit more complex and more combinations are possible due to the fact that a gamete will receive one short and one long chromosome of either color (paternal and maternal chromosomes.) Homologues separate independently and it does not matter which member of a pair goes into which gamete.
A dihybrid cross can form four pair of possible types of gametes. The dihybrid phenotypic ratio is 9:3:3:1.

www.anselm.edu/.../jpitocch/genbio/indassort.JPG

Genetic disorders can be autosomal dominant: an individual with the alleles AA or Aa will have the disorder, or autosomal recessive: an individual with the alleles aa will have the disorder. Some of the more common autosomal recessive disorders are:

• Tay-sachs- lack of the enzyme hexosaminidase A (Hex A) and the storage of the substrate glycosphingolipid in lysomes
• Cystic Fibosis- chloride ions fail to pass through a plasma membrane channel protein in cells, which interferes with the function of the lungs and pancreas
• Phenylketonuria (PKU)- affects the nervous system development due to a lack of the enzyme phenylalanine
• Sickle Cell- the red blood cells are not bi-concave disks and have an irregular shape causing anemia, poor circulation, and low resistance to infection

Some common autosomal dominant disorders are:

• Marfan Syndrome- a defect in an elastic connective tissue protein called fibrillin
• Huntinton Disease- a neurological disorder that leads to the degeneration of brain cells caused by a mutated copy of the gene for protein, huntintin

Polygenic traits are governed by several sets of alleles. Each dominant allele codes for a product and therefore the dominant alleles have a quantitative effect on the phenotype. The result is continuous variation of the phenotypes. Skin color is an example of a polygenic trait.

courses.bio.psu.edu/.../figure_14_12.gif

Incomplete dominance occurs when the heterozygote is intermediate between the two homozygotes. Codominance occurs when alleles are equally expressed in a heterozygote. When traits are controlled by multiple alleles the gene exists in in several allelic forms.

Males and females have 23 pairs of chromosomes, 22 are autosomes, 1 is the sex chromosome. Traits controlled by the genes on the sex chromosome are sex-linked: an allele on the X chromosome is X-linked, an allele on the Y, Y-linked. Most sex-linked disorders are carried on the X chromosome.

Some X-linked recessive disorders are:

• Color blindness
• Muscular Dystrophy
• Hemophilia

www.merck.com/.../figures/MMHE_01_002_03_eps.gif



DNA Biology and Technology

DNA is the genetic material and found in the chromosomes. Genetic material must be able to do 3 things: replicate so it can be transmitted to the next generation, store information, and undergo mutations that provide genetic variability.

DNA is a double helix, composed of 2 strands that spiral around each other. Each strand is a polynucleotide, because it is composed fo a series of nucleotides: a molecule composed of 3 subunits- phosphoric acid (phosphate), a pentose sugar (deoxyribose), and a nitrogen-containing base. The bases of the structure are held together by complementary paired bases. The bases are important to the functioning of DNA and are paired as follows: the purines, Adenine (A) or Guasine (G) with the pyrimidines, Thymine (T) and cytosine (C). The 2 strands of DNA run anti-parallel, or opposite directions.



cache.eb.com/eb/image?id=6520&rendTypeId=4

The process of copying the DNA helis is called DNA replication. During replication, the double-strand structure allows each origianl strand to serve as a template for the formation of a new complementary strand. Rarely, a mutation may occur, causing the sequence of the bases in the new strand different from the parental strand. Usually the error is fixed by enzymes, but that is not always the case.

faculty.uca.edu/~johnc/DNA%20replication.gif

RNA is made up of nucleotides containing the sugar ribose. The only difference nucleotide wise in RNA than DNA is that the base thymine (T) was replaced with uracil (U.) RNA is single stranded, but may double back on itself. Complementary base pairing still occurs.

Ribosomal RNA (rRNA) is produced in the nucleolus of a nucleus where a portion of DNA serves a template for its formation. rRNA joins with proteins made in the cytoplasm when protein synthesis is about to begin. Messenger RNA (mRNA) is produces in the nucleus where the DNA served a a template for its formation. mRNA carries genetic information from DNA to the ribosomes in the cytoplasm. Transfer RNA (tRNA) is produced in the nucleus and transfers amino acids are joined forming a protein.

DNA provides the cell with a blueprint for synthesizing the proteins. Proteins are composed of subunits called amino acids. 20 different amino acids are commonly found in the proteins, which are synthesized at the ribosomes. Proteins determine the structure and function of the various cells in the body.

The first step in gene expression is transcription: a strand of mRNA forms that is complimentary to a portion of DNA. Transcription means "faithful copy." The second step is translation. Translation means to put the information into a different language. In this case, a sequence of nucleotides is translated into the sequence of amino acids.

www.accessexcellence.org/RC/VL/GG/ecb/ecb_ima...

Transcription begins when the enzyme RNA polymerase opens up the DNA helix just in front so that a complementary base pairing can occur. The RNA polymerase joins the RNA nucleotides and an mRNA molecule forms. The mRNA must be processed before entering the cytoplasm. The mRNA becomes mature mRNA. During translation, transfer RNA molecules bring amino acids to the ribosomes where polypeptide synthesis occurs. Polypeptide syntheis has 3 steps:

• Initiation- mRNA binds to the smaller of the 2 ribosomal units;then the larger subunit associates with the smaller one
• Elongation- the polypeptide lengthens one amino acid at a time, an incoming tRNA amino acid complex arrives at the A site and receives the peptide from the outgoing tRNA
• Termination- occurs at the codon that means stop and does not code for an amino acid, the ribosome dissociates into 2 subunits and falls off the mRNA molecule

All cells receive a copy of all genes, however they differ as to which genes are actively expressed. A variety of mechanisms regulate gene expression and they are grouped into four levels:

• Transcriptional control- in the nucleus, a number of mecnanisms regulate which genes are transcribed and the rate at which transcription occurs
• Posttranscriptional control- occurs in the nucleus after DNA is transcribed adn mRNA is formed
• Translational control- occurs in the cytoplasm after the mRNA leaves the nucleus adn before there is a protein product
• Posttranslational control- occurs in the cytoplasm after protein synthesis

A person's genome can be modified. Gene therapies such as ex vivo gene therapy or in vivo gene therapy can treat different medical conditions. The human genome has been sequenced as have genomes of other organisms.

Functional genomics is the study of how the 25,000 different genes in the human genome function. Comparative genomics is a way to determine how species have evolved and how genes and noncoding regions of the genome function.

Protemics is the study of the structure, function, and interaction of cellular proteins. Bioinformatics is the application of computer programs to the study of the genome.

Citations:

Biology Project: Cell Biology. (2008) http://www.biology.arizona.edu/CELL_BIO/cell_bio.html



Folding @ Home Distributed Computing. (2008) http://folding.stanford.edu/English/Science



Hyperphysics:Chemical Bonding. (2008) http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html



Mader, S. (2008) Exploring Life and Science, Chemistry of Life, Cell Structure and Function, and
Regulation and Organization of Body Systems. Human Biology, 10th ed. (p 1-84)


Microbiology. (2008) http://www.scienceprofonline.org/

Compendium Review-Cells and Genetics

Table of Contents

Exploring Life And Science
Chemistry of Life
Cell Structure and Function Organization
Organization and Regulation of Body Systems

Exploring Life and Science

Biology is the scientific study of life and human biology is a specialty in this field. Human beings are part of the natural world. All living things share the characteristics of life:

• are organized, from atoms to the biosphere
• take materials and energy from the environment
• reproduce
• grow and develop from fertilization to death
  
• are homeostatic
• respond to stimuli
• have an evolutionary history and have adapted modifications to a particular way of life

www.spacetoday.org/.../TerraAqua/TerraStory.html

Atoms join together to form molecules that make up cells. A cell is the smallest structural and functional unit of an organism. Human beings are multicellular: composed of many different types of cells. A tissue is a group of cells that perform a particular function. Several types of tissue make up an organ and each organ belongs to an organ system. Organisms are a collection of of organ systems.

Levels of biological organization extend beyond the individual. A species is a group of interbreeding organisms in a particular area that belong to a population. Populations of various animals and plants make up a community. The community of populations interact with the physical environment to form an ecosystem and in turn, all the ecosystems of earth form the biosphere.

Reproduction is a fundamental characteristic of life. Living things reproduce and create a copy of themselves. The presence of genes in the form of DNA allow cells and organisms to reproduce. DNA contains the hereditary information that direct the cell structures and the metabolism, all the chemical reactions in the cell. DNA replicates so exact copies of genes are passed to the offspring.

www.scq.ubc.ca/wp-content/dna.gif

Development in humans includes the changes from egg fertilization until death. Development also encompasses repair that takes place after an injury.

Organs maintain homeostasis: an internal environment that varies within certain limits. All systems of the human body assist in maintaining homeostasis. Living things respond to external stimuli, often by moving toward or away from the stimuli. Homeostasis would be impossible without the body's ability to respond to stimuli.

Evolution is the process by which a species changes through time. Adaption is the process by which the species changes, by each successive generation, to variation. Evolution has been ongoing since the origin of time and will continue.

Living things are classified into three domains: Eukarya, Archaea, and Bacteria. Domain Eukarya contains four kingdoms: Animalia (including humans,) Plantae, Fungi, and Protista.

faculty.southwest.tn.edu/rburkett/classi6.jpg

Culture encompasses human activity and products that are passed on from one generation to the next. Among animals, only humans have a language that allows us to communicate information and experiences symbolically.


All living things on Earth are part of the biosphere: a living network that spans the surface of the earth from the atmosphere to the soil and sea. The human population tends to modify existing ecosystems for their own purpose. Almost all natural ecosystems are altered by human activities, reducing biodiversity. Extinction is the death of a species or larger group of organisms.

http://www.valeofglamorgan.gov.uk/living/environment/biodiversity.aspx

Science is a way of knowing about the natural world. Scientists aim to be objective, rather than subjective. Scientific theories are concepts that tell us about order and pattern within the natural world. Evolution is the unifying concept of biology.

http://brasilmagic.wordpress.com/2007/10/

Scientific information is acquired through the process of the scientific method. The scientific method has five steps: observation, hypothesis, experiment/observations, conclusion, and scientific theories. Scientists perform controlled experiments to test their hypothesis and upon conclusion, publish their results.

http://www.sciencebuddies.org/mentoring/project_scientific_method.shtml

When evaluating scientific studies, consider the type of data which supports the information. Graphs and statistical data are important, as is the methodology of the study.

Science is a systematic way of acquiring knowledge. Scientists should avoid value judgments of experiments. Modern technology has risks and everyone should make informed decisions regarding how and when technology should be used.


Chemistry of Life



Matter refers to anything that takes up space and has mass. An element is one of the basic building blocks of matter that cannot be broken down by chemical means. An atom is the smallest unit of element that retains the chemical and physical properties of the element.




http://www.rfcafe.com/references/general/periodic_table.htm


The subatomic particles of an atom located in the nucleus are the protons and neutrons. The electrons orbit around the nucleus shell. Protons have a positive charge and electrons have a negative charge. The atomic number for an element tell you how many protons there are. The atomic mass for an atom allows you to determine the number of neutrons.

















http://www.chem4kids.com/files/atom_structure.html
http://www.chem4kids.com/files/atom_structure.html


Isotopes of the same type of atom differ in the number of neutrons, therefore mass. Radioisotopes release radiation during the breakdown of the isotope. Different levels of radiation play a part in biology from tracer isotopes to the destruction of malignant cells.

Atoms bond with one another to form molecules. There are two different types of bonding: ionic bonding and covalent bonding. During ionic bonding, atoms give up or take electrons in order to achieve a stable outer shell. During covalent bonding the atoms share electrons.

http://www.freethought-forum.com/forum/showthread.php?t=11572&garp

Water is the most abundant molecule in living organisms, usually making up 60-70% of total body weight. Water is a polar molecule, the oxygen end has a slight negative charge and the hydrogen a slight positive charge. A hydrogen bond occurs when a covalently bonded hydrogen is slightly positive and attracted to a negatively charged atom some distance away. Water molecules are cohesive and have beneficial characteristics:

• Water is a liquid at room temperature.
• The temperature of water rises and falls slowly.
• Water has a high heat of vaporization.
• Frozen water is less dense than liquid ice.
• Water molecules are cohesive.
• Water is a solvent for polar molecules.

http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/notes/chpt2/waternotes.html

Ions and molecules that interact with water are hydrophilic. Nonionized and nonpolar molecules that do not are hydrophobic.

When water molecules dissociate, they release an equal number of hydrogen ions and hydroxide ions. The dissociation is measured in moles. A mole is a unit of scientific measurement for atoms.

Acidic solutions have a high H+ concentration. Base solutions have a low H+ concentration. The pH scale is used to indicate the acidity or alkalinity of a solution. Pure water with an equal number of hydrogen and hydroxide ions has a pH of 7.

http://bcn.boulder.co.us/basin/data/BACT/info/pH.html

In living things, the pH of body fluids needs to be maintained within a narrow range. The body and environment have buffers to prevent pH changes. Buffers are chemical combinations that keep the pH within normal limits due because they are chemical or combinations that take up excess hydrogen or hydroxide ions.

The four classes of molecules unique to cells are carbohydrates, lipids, proteins, and nucleic acids. Each molecule is composed of subunits called macromolecules. Macromolecules are created by a dehydration reaction in which a hydroxyl group and a hydrogen atom are removed as the molecule reforms. To breakdown a macromolecule, a hydrolysis reaction is used.

Carbohydrates (H-C-OH) are molecules in which the ratio of hydrogen atoms to oxygen atoms is about 2:1.
Monosaccharides have between 3 and 7 carbon atoms. A disaccharide is made by by joining two monosaccahrides together by the dehydration reaction. Polysaccharides contain many glucose units.

http://science9.wordpress.com/2007/04/

Lipids contain more energy per gram than other biological molecules. Lipids do not dissolve in water and contain little oxygen. The most familiar lipids are fats (animal)and oils (plant.) Emulsifiers can cause fats to mix with water. There are different kinds of fatty acids: saturated, unsaturated, and trans fats.

http://www.biosynth.com/index.asp?topic_id=221&g=19&m=272

Phospholipids are constructed like fats, but have a phosphate group in place of the third fatty acid. They are primary components of cellular membranes. Steroids are lipids that have an entirely different structure than fats. Cholesterol is a precursor of several steroids.

Proteins are important in the structure and function of cells. Proteins have many functions in humans:

• Support
• Enzymes
• Transport
• Defense
• Hormones
• Motion

Proteins are macromolecules with amino acid subunits. Amino acids differ according to their R group. Peptide bonds are a result of two amino acids that have joined together by dehydration. Proteins cannot function without their usual shape. If exposed to extremes and irreversible change in shape called denaturation occurs.

http://publications.nigms.nih.gov/structlife/chapter1.html

There are two types of nucleic acid: DNA and RNA. DNA and RNA are polymers of nucleotides. Every nucleotide is a molecular complex of three subunit molecules: phosphate, a pentose sugar, and a nitrogen contaning base. DNA contains deoxyribose sugar and RNA contains ribose. DNA has four different bases: adenine, thymine, guanine, and cytosine. In RNA uracil replaces thymine. The nucleotides form a strand which has a phosphate-sugar-phosphate-sugar backbone. DNA is double stranded and RNA has a single strand.

http://www.acmecompany.com/Pages/stock_science.html

Cell Structure and Function Organization

Organisms, including humans, are composed of cells. One of the fundamental principles of modern biology is the cell theory. The cell theory states that a cell is the basic unit of life. Nothing smaller than a cell is alive. Life has a cellular nature.

• All living things are made up of cells
• New cells arise only from preexisting cells

www.cellsalive.com/cells/cellpix/cell_model.jpg

Most cells are not visible to the naked eye. The small size of cells are explained by the surface area to volume ratio. Nutrients enter a cell and waste exits at its surface, therefore the greater the ability to get material in and out of the cell. Larger cells require more nutrients. However, the larger a cell gets in volume, the proportionate amount of surface area decreases.


staff.jccc.net/pdecell/cells/surface.gif

Micrographs and photographs of objects are obtained using a compound light microscope, a transmission electron microscope, of a scanning electron microscope. A compound microscope uses a set of glass lenses and light rays passing through the eye to magnify objects. A transmission electron microscope has a higher rate of magnification and higher resolving power: the ability to make out detail in enlarged images. A scanning electron microscope provides a three dimensional view of the surface of an object. The light microscope is the only one to view living specimens as the electron microscope must maintain a strong vacuum.

www.hometrainingtools.com/misc/compound%20par...

Cells have an evolutionary history. The first cells to arise were prokaryotic cells which lack a nucleus. Bacteria and archaea represent prokaryotic cells. Eukaryotic cells have a nucleus are known for living in extreme environments that mirror the first Earth environments. Both of these cells have a plasma membrane, an outer membrane which regulates what enters the cell. A plasma membrane is a phospholipid membrane which is selectively permeable. All cells also contain cytoplasm: a semifluid medium that contains water and various types of molecules suspended or dissolved in that medium. The cytoplasm contains organelles which are small structures that perform specific functions.

The internal structure of eukaryotic cells have evolved over time. Unlike prokaryotes, eukaryotes have DNA surrounded by a membrane: the endomembrane system.

micro.magnet.fsu.edu/.../images/animalcell.jpg

The plasma membrane is selectively permeable. It marks the boundary between the inside and outside of a cell. The integrity of the membrane is necessary to cellular life. The plasma membrane is a phospholipid bilayer with attached or embedded proteins. The phospholipid molecule has a p0lar head and nonpolar tails. When placed in water they for a spherical bilayer. The polar head are hydrophilic and the tails are hydrophobic. The plasma membrane keeps the cell intact.

Diffusion is the random movement of molecules from an area of higher concentration to the area of lower concentration, until they are equally distributed. Osmosis is the diffusion of water across the plasma membrane. Tonicity is the concentration of the solute in a solution stated by percentage. Many solutes do not diffuse across the plasma membrane, but are transported by protein carriers. During facilitated transport, a molecule is transported across the membrane at a higher than usual rate to the side of lower concentration. During active transport, a protein carrier and cellular energy from the breakdown of ATP, the molecule moves against the normal travel direction from lower to higher concentration.

kvhs.nbed.nb.ca/gallant/biology/water_balance.jpg




www.linkpublishing.com/exocytosis5.jpg

During endocytosis, a portion of the plasma membrane invaginates to envelop a substance and fluid. The membrane then pinches off to form an endocytic vesicle inside the cell. Some white blood cells take up pathogens during this process: phagocytosis. During exocytosis, a vesicle fuses with the plasma membrane as secretion occurs.

micro.magnet.fsu.edu/.../endocytosisfigure1.jpg

The nucleus is a prominent structure in a cell and stores genetic information. The nucleus is separated from the cytoplasm by a double membrane known as the nuclear envelope.

www.modares.ac.ir/.../week2/nucleus_1%5B1%5D.gif

Ribosomes are organelles composed of proteins and rRNA. Protein synthesis occurs at the ribosomes.

www.williamsclass.com/.../Ribosomes.gif

The endomembrane system consists of the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysomes, and vesicles. The endoplasmic reticulum has two portions. The Golgi apparatus is named for Camillo Golgi who discovered it in 1898.

The cytoskeleton of a cell is composed of several types of protein fibers. It helps maintain the cells shape. Microtubules are much larger than the actin filaments. Each microtubule is a cylinder that contains 13 longitudinal rows of proteins called tubulin. The microtubules are regulated by the cetrosome. Actin filaments are made of protein called actin. They are long thin fibers, usually in bundles or groupings.

Cilia and flagella are involved with movement. Cilia are about 20x longer than flagella, but both have the same organizational structure. Cilia and flagella grow from basal bodies: structures located in centrosomes called centrioles.

Mitochondria are the cells powerhouses. They convert the chemical energy of glucose into the chemical energy of ATP: cellular respiration. Cellular respiration is very important in metabolism: all the chemical reactions which occur in a cell. Cellular respiration includes three pathways: glycolysis, the citirc acid cycle, and the electron transport cycle.

www.nature.com/.../v24/n50/images/1209097f1.jpg

Enzymes speed up the reaction in a cell and are usually named for their substrates. Enzymes have a specific region (active site) where the substrates are brought together to react. Coenzymes are nonprotein the assist the activity of an enzyme and may accept or contribute atoms to the reaction.

Fermentation is an anaerobic process (not needing oxygen.) Fermentation produces little ATP and lactate build up occurs.

staff.jccc.net/pdecell/cellresp/fermentation.gif

Organization and Regulation of Body Systems

A tissue is composed of specialized cells of the same type that perform a common function. The tissues of the human body are categorized into four major types:

www.nlm.nih.gov/.../ency/fullsize/8682.jpg

Connective tissue has 3 components: specialized cells, ground substance, and protein fibers. The fibers are broken into collagen, reticular, and elastic. The cells in both loose fibrous and dense fibrous connective tissues are called fibroblasts. Matrix is the term that includes ground substance and fibers. Loose fibrous connective tissue supports internal organs. Adipose tissue is a special type which the cells enlarge and store fat. Dense fibrous connective tissue contains collagen fibers packed together such as in tendons and ligaments. Supportive connective tissues are the cartilage: hyaline, elastic, and fibrocartilage. Bone is the most rigid of connective tissues. The matrix consists of inorganic salts (mostly calcium) around protein fibers (usually collagen.) Compact bone makes of the shaft of long bones and has cylindrical units called osteons. Spongy bone appears as open, bony latticework with numerous bony bars and plates. Fluid connective tissues consist of blood and lymph. Blood consists of erythrocytes, leukocytes, and thrombocytes. Lymph is a clear, watery fluid that contains white blood cells.

http://www.daviddarling.info/images/types_of_connective_tissue.jpg

Muscular Tissue is composed of cells called muscle fibers. Muscle fibers contain protein filaments called actin and myosin filaments. The 3 types of vertebrate tissue are skeletal, smooth, and cardiac.
Nervous tissue consist of nerve cells and neuroglia. Neurons are specialized cells that consist of dendrites, a cell body, and an axon. A dendrite is an extension that receives signals from sensory receptors. The cell body contains most of the cell's cytoplasm and the nucleus. The axon is an extension that conducts nerve impulses. Long axons are covered by myelin. Outside the brain and spinal cord, fibers bound by connective tissue are called nerves. Neuroglia are cells that outnumber neurons 9:1 and take up more than half the volume of the brain. The primary function is to is to support and nourish neurons. Types of neurons in the brain are microglia, astrocytes, and oligodendrocytes.

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/neurons_1.gif

Epithelial tissue covers the body and lines its cavities. There are different types of epithelial tissue:

• Simple sqaumous
• Simple cuboidal
• Simple columnar
• Pseudostratified ciliated columnar
• Stratified sqaumous

media.wiley.com/Lux/70/21770.nfg001.jpg

The integumentary system is associated with particular organs. An organ is composed of two or more types of tissues working together. An organ system contains many different organs. Skin is the most conspicuous organ in the body. The skin has 2 regions, the epidermis and dermis. A subcutaneous layer is found between the skin and underlying muscle or bone.

www.racingsmarter.com/.../SkinTissue.jpg


The epidermis is made up of stratified squamous epithelial tissue. New epidermal layers derive from stem (basal) cells. 2 types of specialized cells are located are located deep in the epidermis: Langerhans and the melanocytes. The dermis is a region of dense fibrous connective tissue beneath the epidermis. The dermis contains collagen and elastic fibers. The subcutaneous layer is not really part of the skin, but is composed of loose connective tissue and adipose tissue.

An acronym I use to remember the organ systems is MURDERS INC:

M Muscular system: posture, moves body and internal organs, produces heat
U Urinary System: excretes metabolic waste
R Respiratory system: maintains breathing, exchanges gases at lungs and tissues
D Digestive system: ingests and digest food, absorbs nutirents
E Endocrine system: produces hormones, regulates metabolism
R Reproductive system: produces and transports gametes, produces sex hormones
S Skeletal system: supports the body, protects body parts

I Integumentary System: protects body, receives sensory input, helps control temperature
N Nervous system: receives sensory input, helps coordinate motor systems
C Cardiovascular system: transports blood, nutrients, gases, and waste, defends against disease

www.agen.ufl.edu/.../lect/lect_19/147a.gif

www.agen.ufl.edu/.../lect/lect_19/147b.gif

Homeostasis is the relative constancy of the internal environment, which is tissue fluid and blood. Negative feedback mechanisms keep the environment relatively stable. When a sensor detects change, a control center brings about an effect that reverses the change to bring the system to normal. Positive feedback mechanisms bring about rapid change in the same direction as the stimulus and does not achieve relative stability.

Citations

Biology Project: Cell Biology. (2008) http://www.biology.arizona.edu/CELL_BIO/cell_bio.html

Folding @ Home Distributed Computing. (2008) http://folding.stanford.edu/English/Science



Hyperphysics:Chemical Bonding. (2008) http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html



Mader, S. (2008) Exploring Life and Science, Chemistry of Life, Cell Structure and Function, and
Regulation and Organization of Body Systems. Human Biology, 10th ed. (p 1-84)


Microbiology. (2008) http://www.scienceprofonline.org/


Water Molecule. (2008) http://www.aquadyntech.com/watermolecule.html