DNA (deoxyribonucleic acid) is a molecule that carries the genetic information in the cells of living organisms, controlling their functioning and inheritance of their characteristics. Human DNA determines the way our bodies grow and develop from the day we are conceived. Technically, due to its consistency and governing role it has in our bodies, DNA can be used to clone a human being from a strand of hair, a drop of blood, or by his or her sweat. The basic chemicals DNA is composed of are, nitrogen, oxygen, hydrogen, and carbon and phosphorous. Nucleotides are chemical building blocks of every DNA molecule.
Each nucleotide contains sugars forming a ring. An atom of phosphorous with oxygen atoms around is bonded to one part of this sugar ring. A nitrogenous base is bonded to another part of the sugar and this base is what makes the difference between nucleotides.
There are four types of nitrogen bases found in nucleotides: adenine (A), thymine (T), guanine (G) and cytosine (C). The DNA bases form twisted ladder shape called a “double helix”, which is built according to rigid rules – A always pairs with C and T always pairs with G. The order of these bases dictates what biological instructions are contained in a strand of DNA. It works similar to the way in which letters of the alphabet are placed in a certain order to form specific words and understandable sentences.
Nucleotides form DNA strands. This looks like a chain, with the phosphate and sugar groups. These DNA sequences contain instructions on how to make a protein and they are called genes. Human genome contains about 3 billion bases and about 25,000 genes on 23 pairs of chromosomes. Scientists have determined the functions of some of our genes, but there are many whose functions are still unknown.
Each cell in your body has the same DNA and that makes each of us unique. Our cells are able to turn off most genes and work only with those genes necessary to do a certain kind of work, like to build a heart, liver, brain and every other organ of our body. It is going to take a hard work in genetics to explain all aspects of this mechanism