Question

List out the salient features of the human genome project.

Answer 1

Hint: The following goals were set by the HGP.
1. Determine the sequence and number in the human genome of all the base pairs.
2. Identify all the genes found in the genome of humans.
3. Determine all the genes' roles.
4. Identify the different genes that cause genetic disorders.
5. Determine hereditary susceptibility for different diseases and immunity to them.
6. Data storage in databases.
7. Improving data processing software.

Complete Answer:
Methodology: There are two kinds of methods to study the genome,
(i) Classify all the genes that are expressed as sequence tags or ESTs expressed as RNA.
(ii) Sequencing the entire genome (both coding and noncoding regions) and later assigning the various regions with functions -sequence annotation.
(iii) The second approach involving subsequent measures was adopted by HGP.

Salient Features:
1. 3,1647 billion nucleotide base pairs are in the human genome.
2. 3000 base pairs are the typical gene size. The largest gene on the X chromosome is that of Duchenne Muscular Dystrophy. It has 2.4 million base pairs (2400 kilos). The genes for B-globin and insulin are smaller than 10 kilobases.
3. The human genome is made up of 30,000 or so genes. It was historically known to have 80,000 to 100,000 genes in it. The number of human genes is around the same as that of a rodent. Nine-tenths of the genes are similar to mouse genes. We have more than twice the number of genes that are fruitful (Drosophila melanogaster) and six times the number of genes in Escherichia coli.
The size of the genome or number of genes is not correlated with the complexity of the organisation of the organism, e.g., Lily has 18 times more DNA than the human genome, but since its DNA has more introns and less exons, it produces less protein than us.
4. Chromosome I has 2968 genes, while there are 231 genes in the Y-chromosome. These are the maximum and minimum genes for the chromosomes in humans.
5. The function of over 50 percent of the genes discovered is unknown.
6. Structural genes that code for proteins constitute less than 2 percent of the genome.
7. In all human beings, 99.9 percent of the nucleotide bases are exactly identical.
8. With some 3.2 million nucleotides, only 0.1% of the human genome reflects the heterogeneity found in human beings.
9. Single nucleotide variations called SNPs (snips) or single nucleotide polymorphisms exist at around 1.4 million sites. They have the ability to help find chromo­somal locations for disease related sequences and tracing human history.
 10. A significant portion of the human genome is made up of repeated or repetitive sequences. There are some 30,000 minisatellite loci, each of which has 11-60 bp tandemly duplicated up to 1,000 times. There are approximately 2,00,000 microsatellites, each with up to 10bp repeat of 10-100 times.
11. Nucleotide sequences are repetitive sequences replicated several times, often hundreds to thousands of times. They do not have a clear coding feature, but provide details on the structure, dynamics and evolution of chromosomes.
12. Approximately 1 million copies are clustered around centromeres and near chromosome ends of repeated sequences of brief 5-8 base pairs. DNA garbage represents them.

Note: The variations in genetic makeup are due to differences in their DNA nucleotide sequences. Therefore, scientists have always had the ambition to map the human genome. Advances in genetic engineering techniques have allowed DNA pieces to be separated and cloned and nucleotide sequences of these fragments to be determined.