Q4. Using only NCERT’s stated historical length figures, how many times longer is dystrophin than its quoted average gene?
2.4 million ÷ 3000 = 800 times (NCERT page 104; our arithmetic).
Q5. Which two approaches did the HGP use, and how do they differ?
The Expressed Sequence Tags (ESTs) approach focused on identifying all the genes expressed as RNA; the sequence-annotation approach sequences the whole genome, coding and non-coding, and assigns functions to regions later (NCERT page 103).
Q6. Why were DNA fragments cloned before they were sequenced?
Cloning in a host amplified each fragment, so that it could then be sequenced with ease; very long DNA cannot be sequenced in one piece, so the DNA was first broken into smaller random fragments (NCERT page 103).
Q7. Name three non-human organisms whose genomes NCERT says have been sequenced.
Any three of bacteria, yeast, the nematode Caenorhabditis elegans, the fruit fly Drosophila, rice and Arabidopsis (NCERT page 103).
Q8. What are SNPs, and about how many such locations have been found in humans?
Single nucleotide polymorphisms, locations where single-base DNA differences occur between people; NCERT’s historical tally is about 1.4 million; this is not the present total (NCERT page 104).