Q.The total number of nitrogenous bases in human genome is estimated to be about

The Human Genome Project

The Human Genome Project (HGP) was a mega-international project launched in 1990 (largely completed in 2003) with the goal of sequencing the entire human genome — about 3 × 10⁹ base pairs — and identifying all its genes.

Its primary aim was to generate two main types of maps:

• Genetic (linkage) maps — the relative positions of genes/markers on chromosomes based on recombination frequencies.
• Physical maps — the actual physical distances between markers, measured in base pairs.

Two main strategies were used: Expressed Sequence Tags (ESTs), focusing on the expressed (gene) portions, and Sequence Annotation (shotgun sequencing), sequencing the whole genome and then assigning function.

Salient findings: the genome contains roughly 20,000–25,000 genes; less than 2% codes for proteins; chromosome 1 has the most genes and the Y chromosome the fewest; and repetitive sequences make up a large fraction. …