The term genome (introduced by H. Winkter in 1920) refers to one complete copy of the genetic information (DNA) or one complete set of chromosome (monoploid or haploid) of an organism. The term genomics (term coined by T.H. Roderick in 1987) denotes mapping, sequencing and functional analysis of genomes.
The Human Genome Project (HGP) was launched on 1st October, 1990 for sequencing entire genome of 2.75 billion nucleotide pairs. This megaproject was a 13 year project coordinated by the U.S. Department of Energy and the National Institute of Health. During the early years of the HGP, the Wellcom Trust (U.K.) becomes a major partner; additional contributions come from Japan, France, Germany, China and others.
The project was completed in 2003. James Watson was the first directors of human genome project and after a period of two years he was replaced by Francis Collins in 1993. Two important scientists associated with HGP were Francis Collins, director of the HGP and J. Craig Venter, founding president of Celera Genomics. HGP was closely associated with rapid development of a new era in biology called as Bioinformatics.
Goals of Human Genome Project:
Human Genome Project had many goals some of the important goals were outlined below:
1. To identify all the approximately 20,000-25,000 genes in human DNA.
2. To determine the sequences of the 3 billion base pairs that makes up human DNA.
3. To store this information in data base.
4. To develop improvised tools for data analysis.
5. To transfer related technologies to other sectors, such as industries.
6. To address the ethical, legal and social issues (ELSI) that may arise from the project.
The methodologies involved two major approaches identifying all genes of the genome and their sequencing. For sequencing, the total DNA from a cell is isolated and converted into fragments of relatively small sizes and cloned in suitable host, this generates a genomic library of the organism. The complete sequencing of the first human chromosome, small chromosome 22, was published in December 1999. Then chromosome 21 was completely sequenced in May 2000. The first draft sequence of entire human genome was published in the famous scientific journal “Nature” on 16th February, 2001.
Important Features of Human Genome:
1. The human genome contains 3164.7 million nucleotide bases.
2. The average gene consists of 3000 bases, but gene size vary greatly (the largest human gene is dystrophin containing 2.4 million bases).
3. The total number of genes in the genome is estimated at 30,000 and all (99.9 percent) nucleotide bases are exactly the same in all people
4. Functions of about 50% of the discovered genes are still unknown.
5. Less than 2% of the genes of the genome codes for proteins.
6. Chromosome 1 has most genes (2968) and the Y has the fewest (231).
7. Repeated sequences (AT-AT-AT or GC-GC-GC…….) make up very large portion of the human genome.
8. Scientists have identified about 1.4 million locations where single base DNA differences (SNPs-single nucleotide polymorphism, pronounced as ‘snips’) occur on humans.
Human Genome Project was an undertaking by many countries to acquire complete knowledge of the organisation, structure and functions of the human genome. Such a multinational undertaking was called as International Human Genome Sequencing. HGP was regarded as the most ambitious project ever undertaken by humans.
The project had the benefits to identify all human genes and also mutated genes causing diseases. Complete knowledge on the genome sequence will enable the scientists in future to gain knowledge on the types of proteins encoded by these genes. The cloning and sequencing of the disease causing alleles (mutated genes) will largely help in the diagnosis and treatment of diseases.