Haplotype blocks can be seen in humans because _______

Question

(a) disease genes are found in haplotype blocks.
(b) modern humans descended from a relatively small population of about 10,000 individuals that existed about two thousand generations ago.
(c) some of our human ancestors interbred with Neanderthals.
(d) new mutations cannot be introduced into existing haplotype blocks.

Answer 1

(b) The relatively small population of human ancestors means that the chromosomes in modern-day humans are a shuffled set of a relatively small number of chromosome sets. Because this small population existed only about two thousand generations ago, there hasn't been enough time for recombination to scramble these haplotype blocks. Disease genes can certainly be found in haplotype blocks [choice (a)], although this is not why haplotype blocks exist. Although genome analysis does show that some ancestors of modern humans did interbreed with Neanderthals, this is not the main reason for the existence of haplotype blocks [choice (c)]. New mutations can be introduced into an existing haplotype block, so choice (d) is untrue.