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Home About DNA Sources

Table of contents

- DNA Structure - DNA Replication - DNA as Evidence

DNA Structure

This is a chromosome. ("Chromosome")

A chromosome is made up of a protein that has DNA coiled around it. (Shuster)

This is what DNA looks like, (well, sort of). Each side is made up of a set of nucelotides, which contains a phosphate (green), sugar (red), and a base (white). Two nucelotides form a hydrogen bond based on their base (adenine (A) matches with thymine (T) and guanine (G) with cytosine (C).) In humans, over 99% of DNA is the same, but the remaining DNA normally reffers to certain traits, i.e. blue eyes or black hair.(Hardin; Shuster)

DNA Replication

The helicase breaks apart the bonds and unwinds the DNA. The topoisomerase (not shown) is also used to cut the DNA strand and relax the electrons.

The polymerase attaches nucelotides to the other set of nucelotides.

(Shuster; Nitiss)

DNA cal also be replicated in a lab with a process called PCR. In this process, DNA, nucelotides, polymerase, and primers are placed inside a machine that repeatedly heats and cools them. Each type that cycle is repeated, the number of DNA doubles. After 30 times, there's over a billion DNA. (Shuster)

DNA as Evidence

First, evidence is collected from the crime scene. In many cases, this take the form of blood, hair, and skin particles.

The DNA collected is put through PCR, which was discussed in the DNA replication section. This creates billions of copies of the DNA for forenstic scientists to analyze.

After the DNA is put through PCR, the sample from the crime and samples from possible suspects are put through gel electrophoresis, which measures the short tandum repeats (STR's) of a persons DNA. This can be used to accuratly identify the person who commited the crime.

(Shuster)