Ncert Exercises & Solutions

Q. 5. The total number of genes in human is far less(<25000) than the previous estimate (up to 14000 gene). Comment.

Ans. The total number of genes is estimated at 25000 much lower than previous estimates of 140000 that had been based on extrapolations from gene-rich areas as opposed to a composite of gene-rich and gene-poor areas.

Almost all (99.9%) nucleotide bases are exactly the same in all people. Functions for over 50% discovered genes are not known yet. Scientists have identified about 1.4 million locations where sinlge-base DNA difference (SNPs or Single Nucleotide Polymorphisms) occur in humans.

This information promises to revolutionise the processes of finding chromosomal locations for disease-associated sequence and tracing human history.

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