A genome is an organism's complete set of DNA, the chemical compound that contains the instructions needed to develop and direct the activities of nearly all living organisms. They are made of two twisting, paired strands often referred to as a double helix. Each DNA strand is made of four chemical units, called nucleotide bases, which comprise the genetic "alphabet."

Virtually every single cell in the body contains a complete copy of the approximately 3 billion DNA base pairs, or letters, that make up the human genome. DNA contains the information needed to build the entire human body.

Scientists identified 3.055 billion base pairs (“letters”) of our DNA code as they made the data public. However, the wait has been over two decades since the first draft was released in 2001. Scientists have known for decades that genes were spread across 23 pairs of chromosomes.

As long stretches of the genome remained unknown , scientists struggled to understand where millions of bases fit. While they released the first draft in 2001, the reference genome draft was released in 2013 where they had read these fragments more accurately.

The Human Genome Project that first realised its goal in 1988 aimed to decipher the human genome in three major ways:

• Determining the order, or "sequence", of all the bases in our genome's DNA
• Making maps that show the locations of genes for major sections of all our chromosomes
• Producing what is called linkage maps, through which we inherit trait

The project has revealed that there are probably about 20,500 human genes and the information about their structure, organization and function can be "thought of as the basic set of inheritable 'instructions' for the development and function of a human being."

A startling finding of this first draft was that the number of human genes appeared to be significantly fewer than previous estimates, which ranged from 50,000 genes to as many as 1,40,000.