The Human Genome Project was an international collaborative research project to sequence the human genome – find the exact order of nucleotides (chemical base units) that make up all of human DNA (deoxyribonucleic acid)
A genome is an organism’s complete set of deoxyribonucleic acid (DNA), a chemical compound that contains the genetic instructions needed to develop and direct the activities of every organism. DNA molecules are made of two twisting, paired strands. Each strand is made of four chemical units, called nucleotide bases. The bases are adenine (A), thymine (T), guanine (G) and cytosine (C). Bases on opposite strands pair specifically; an A always pairs with a T, and a C always with a G.
In short, the genome is divided into chromosomes, chromosomes contain genes, and genes are made of DNA.
Every person has a unique genome. The genome differences between two people are much smaller than the genome differences between people and our closest relatives, the chimpanzees. The human genome contains approximately 3 billion of these base pairs, which reside in the 23 pairs of chromosomes within the nucleus of all our cells. Each chromosome contains hundreds to thousands of genes, which carry the instructions for making proteins. Each of the estimated 30,000 genes in the human genome makes an average of three proteins.
Every cell in our body contains 23 pairs of chromosomes, within its nucleus. Each chromosome in each pair comes from the either parent. One pair of chromosomes, called the sex chromosomes, determines the sex of the person – males have XY pair whereas females have XX pair.
Some definitions are in order:
Genome: An organism’s complete set of genetic instructions. Each genome contains all of the information needed to build that organism and allow it to grow and develop. Our genome is approximately 3,000,000,000 base pairs long and is packaged into 23 pairs of chromosomes.The human genome contains 20,687 protein-coding genes.
Genes: Genes are small sections of DNA within the genome that code for proteins. They contain the instructions for our individual characteristics – like eye and hair colour.
Chromosome: A threadlike structure in our cells, made of a long DNA molecule, wrapped around a protein scaffold. Humans have 23 pairs of chromosomes.
DNA: DNA or deoxyribonucleic acid is a long molecule that contains our unique genetic code. Like a recipe book it holds the instructions for making all the proteins in our bodies.
The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human 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.