DNA(or more formally:

Deoxyribonucleic Acid)

By Caitlin and Audrey

Basic Information• DNA is a double helix formed by base pairs attached to a polymer (sugar-phosphate) backbone.• Most DNA is located in the cell nucleus (but a small amount of DNA can also be found in the mitochondria)• The information in DNA is stored as a code made up of four chemical bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T).

Fun FactHuman DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.

Basic Information Continued

DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule (the long swirly strands) to make the double helix structure

A TC G

Making ProteinsSTEP 1: Transcription. In this

process, the information stored in a gene’s DNA is transferred to a similar molecule called RNA (ribonucleic acid). The type of RNA that contains the information for making a protein is called messenger RNA (mRNA) because it carries the information, or message, from the DNA out of the nucleus into the cytoplasm.

STEP 2: Translation is getting from a gene to a protein, and this takes place in the cytoplasm. The mRNA interacts with a ribosome, which “reads” the sequence of mRNA bases. Each sequence of three bases, called a codon, usually codes for one particular amino acid. (Amino acids are the building blocks of proteins.) A type of RNA called transfer RNA (tRNA) assembles the protein, one amino acid at a time.

Most genes contain the information needed to make functional molecules called proteins. The journey from gene to protein is complex and tightly controlled within each cell. It consists of two major steps: transcription and translation. Together, transcription and translation are known as gene expression.

The RNA opens DNA to copy the

DNA’s information, acting like a

zipper. Then once transported to the cytoplasm, in the

Ribosome, the tRNA assembles the protein one amino acid at at

time.

Genetics Example: Skin Color

Scientists have figured out that several genes are involved in skin color.

1. One of these genes is the melanocortin 1 receptor (MC1R). When MC1R is working well, it converts pheomelanin* into eumelanin*. If it’s not working well, then pheomelanin builds up, resulting in freckles.

*Eumelanin is black or brown pigment and pheomelanin is red or yellow pigment.

Two other skin color genes were first identified in fish.

2. Researchers studying the stickleback fish found that the kit ligand gene (kitlg) was different between dark and light stickleback fish. They also found that humans have different versions of this gene too and that certain versions lead to lighter skin. The kit ligand gene is needed for the survival of melanocytes. So if a person (or a fish) has a version of this gene that doesn’t work well, their melanocytes won’t survive as well. Fewer melanocytes will mean less pigment. And so lighter skin.

Fun Fact: Scientists have figured out that lighter skinned East Asians get their skin color mostly from a non-working version of kitlg.

Genetics Example: Skin Color Continued

3. Researchers studying zebrafish with light colored stripes found another gene involved in human skin color, SLC24A5. The fish with light colored stripes had a version of this gene that didn’t work well. When they looked in people, researchers found that some lighter skinned people also had a poorly working version of this gene.

Fun Fact: Northern European people with lighter skin often have a poorly working version of SLC24A5.

These are just some of the genes that researches know of that effect skin color. More than likely, a ton more exist. This serves as one example of how DNA’s sequence of base pairs play out in our traits.

Punnett Square

it is a diagram that illustrates the prediction of the outcome of a cross

it is named after Reginald Punnett, the creator of the method

it is most commonly used to determine or predict the probability of producing offspring of a particular genotype

Punnett Square Continued

There are two types of Punnett Squares:

Monohybrid Cross

Dihybrid Cross

DNA Deformities

When the RNA does not copy correctly, deformities can occur

Example: 1p36 SyndromeA congential genetic disorder or deformity that

Is characterized by intellectual disability Seirzures Limited speech ability

It is caused by a genetic deletion, which is the loss of a DNA segmentThe most common of the deletion syndromes

Traits Inherited Through DNA

Personality traits or habits can be inherited through DNA

There is a strong association of the A1 allele and the DRD2 gene in the alcoholism trait

This basically means that children of one or more parents that are dependent upon alcohol are 50% more likely to develop the problem

Forensic DNA Testing

DNA tests are the more powerful piece of evidence that a lawyer can have

Samples are taken from the crime sceneHair, Skin, Bodily fluids

Samples are also taken from the suspect.

They DNA samples are then taken from each, and if the DNA matches, then the suspect is guilty as charged.

Sources

http://ghr.nlm.nih.gov/handbook/basics/dna

http://www.biologycorner.com/worksheets/DNAcoloring.

html

http://www.thetech.org/genetics/ask.php?id=288

http://en.wikipedia.org/wiki/Punnett_square

http://web4health.info/en/answers/add-alcohol-inherited.htm

http://library.thinkquest.org/28599/courtroom.htm

http://en.wikipedia.org/wiki/DNA