What is DNA ?

DNA is a molecule that contains the instructions an organism needs to thrive. These instructions are found inside every cell as are passed down from parent to their children.

DNA is made up of molecules called nucleotides. Inside each nucleotide there IA a phosphate group, a sugar group , and a nitrogen base. The order of these bases determines the genetic code. Very much like the letters of the alphabet are used to make words, the order of the nitrogen bases form genes. Genes tell cells how to make protein. Another type of nucleic acid RNA ( ribonucleic acid) transmits genetic info from DNA into proteins.

The human genome or the complete set of genetic information for humans, contains about 3 billion bases and about 20 thousand genes. 

Nucleotides are attached together to form a spiral of two long stands called the Double Helix. If you imagine a ladder, phosphate and sugar would be on the sides and the bases would be the rungs. The bases from each side pairs with the base on the other side: adenine with Thymine and Guanine with Cytosine. 

DNA is coiled tightly to form structures called chromosomes. Each chromosome contains one DNA molecules . Humans have 23 pairs of chromosomes.

DNA was first discovered by German biochemist Frederich Miescher in 1869. Not until 1953, did James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin find the structure of DNA- the Double Helix. They realized it could carry biological info. In 1962, they were awarded the Nobel Prize in Medicine.

DNA contains info about your heritage and therefore could help predict if you may be at risk of any diseases. DNA teats are used for many reasons. For example, to diagnose genetic disorders, that were passed down many generations, to determine if a certain person is a carrier of a genetic mutation that they could pass down to they children,  and to examine whether a person is at risk for a genetic disease. 

SOURCE(S): http://www.livescience.com/37247dna.html

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