Biology · Molecular Basis of Inheritance · NEET
NCERT lists six goals: (i) identify all the approximately 20,000 to 25,000 genes in human DNA; (ii) determine the sequence of the 3 billion base pairs of human DNA; (iii) store this information in databases; (iv) improve tools for data analysis; (v) transfer related technologies to industries; and (vi) address the ethical, legal and social issues (ELSI). For NEET, remember the first two are the core scientific goals and ELSI is often asked as the ethical goal.
These are the two methodologies (approaches) of HGP. ESTs (Expressed Sequence Tags) focus only on the genes that are expressed as RNA. Sequence Annotation is the 'blind approach' that sequences the WHOLE genome (both coding and non-coding DNA) first, and later assigns functions to the different regions. So ESTs = genes only; Annotation = everything, then labelled.
The blind approach is another name for Sequence Annotation. Here scientists did not target genes first. They simply sequenced the entire set of the genome (all coding and non-coding sequences) and only later assigned functions to the different regions. NEET has directly asked this exact wording, so link 'blind approach + whole genome + assign functions later = Sequence Annotation'.
The total DNA from a cell was cut into small random fragments and cloned in host cells to amplify (make many copies) so each fragment could be sequenced easily. The common hosts were bacteria and yeast. The vectors used were BAC (Bacterial Artificial Chromosomes) and YAC (Yeast Artificial Chromosomes). Memory hook: BACteria to BAC, Yeast to YAC.
The fragments were sequenced using automated DNA sequencers based on a method developed by Frederick Sanger. Note for NEET: Sanger is also credited with developing the method to determine the amino acid sequence of proteins. The overlapping sequences were then aligned by special computer programs, which is why HGP is linked to Bioinformatics.
HGP was launched in 1990 and completed in 2003, so it was a 13-year project. It was coordinated by the U.S. Department of Energy and the National Institute of Health (NIH). The Wellcome Trust (U.K.) was a major partner, with contributions from Japan, France, Germany, China and others.
If a geneticist uses the blind approach for sequencing the whole genome of an organism, followed by assignment of functions to different segments, the methodology adopted by him is called as:
Expressed Sequence Tags (ESTs) refers to:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The human genome has approximately 3 x 10^9 (3 billion) base pairs. One HGP goal was to identify the roughly 20,000 to 25,000 genes in human DNA.
Because of its huge scale. Sequencing 3 billion base pairs at an estimated US $3 per base pair gave a cost near 9 billion US dollars, and storing the data in books would need about 3300 books for a single human cell. This scale needed high-speed computers, giving rise to Bioinformatics.
Bioinformatics is a new area of biology that uses high-speed computers to store, retrieve and analyse the huge amount of DNA sequence data. HGP was closely associated with the rapid development of Bioinformatics because aligning millions of overlapping fragments was not possible by hand.
ELSI stands for Ethical, Legal and Social Issues. One goal of HGP was to address the ethical, legal and social issues that may arise from the project, such as privacy of genetic data.
No. Many non-human model organisms were also sequenced, including bacteria, yeast, Caenorhabditis elegans (a nematode), Drosophila (fruit fly), and plants like rice and Arabidopsis.
