Final answer:
The human genome contains about 3 billion base pairs of DNA, sequenced by the Human Genome Project, which also identified around 20,000 to 25,000 genes.
Step-by-step explanation:
The human genome consists of about 3 billion base pairs of DNA. This enormous collection of genetic material is contained within 23 pairs of chromosomes and distributed among approximately 20,000 to 25,000 genes. The Human Genome Project (HGP), a monumental international scientific endeavor, sequenced all 3.3 billion base pairs within the human genome and identified these genes. The project, which cost around $3 billion, was completed in 2003, two years ahead of its 15-year projected deadline. While only about 25 percent of the base pairs make up genes and regulatory elements, and only two percent of those actually code for proteins, the remaining sequences have various functions, many of which are still being deciphered by scientists.