You know you've got DNA and you know it can place you at a crime scene, but there's much more to your genetic code than state's evidence.
What is DNA?
DNA is the complete blueprint for you. It is the code that you received from your parents, half from mom and half from pop, that makes you into the organism that you are. Your hair color, your height, the number of fingers you have, how fast your nails grow, it's all programmed into your DNA.
Physical attributes can be affected by environmental factors (hair can be dyed or bleached by the sun, your nutrition can affect various aspects of growth and coloring), but DNA is the code that it's all based on. All living organisms (that we know of) have DNA.
All living creatures have DNA, including dinosaurs, bees, cats, fish, people, and plants.
What is a gene?
Your DNA is broken up into different sections. Genes are pieces of the code that are responsible for production of specific proteins or enzymes. For example, the gene Mc1r is known to be responsible for regulating hair and skin color through the creation of eumelanin. More active Mc1r means darker hair and skin.
Genes are pieces of your DNA that are responsible for pretty much everything that happens in a cell, and therefore pretty much everything that happens in your body.
Genes are made up of combinations of molecules, which scientists represent with the letters A (for adenine), C (for cytosine), G (for guanine), and T (for thymine). These letters pair up to form two strands, where C always stick to G and T always sticks to A. The human genome (all the DNA in one cell) is estimated to be about 3 billion base pairs long.
An example segment of DNA. Each letter represents a nucleotide and the handshake between them represents a hydrogen bond. This drawing is a six-base-pair chain. The human genome is estimated to have 300 billion base pairs.
The two strands and the links between the letters look like a sort of ladder. Take that ladder and twist it over and over, and TAH DAH! you've got that double-helix shape everyone's always talking about.
The "letters" link up to form "words," which are your genes. Your genes link up to form your DNA, which is like the story of you.
Your genes are sections of your DNA, which tells the story of you.
Some genes are made differently in different organisms, and different forms may lead to different results. Different forms of a gene are called alleles. For example, a particular allele of the Mc1r gene leads to less production of eumelanin, and leads to red hair and fair skin.
Scientists have not yet been able to definitively determine how many genes humans have in total.