February_4_2013_NKW

# Thus higher mutaon rate per unit me compared to

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Unformatted text preview: g. 10.14 8 Human ­chimp sequence divergence on diﬀerent chromosomes largely non ­coding 1.  What is the best explana&amp;on for the diﬀerences on X and Y compared to autosomes? 2. How would you es&amp;mate the muta&amp;on rate from this average 1.2% divergence between chimps and humans? NEUTRAL THEORY American Journal of Human Gene&amp;cs 2002 70:1490 Human ­chimp sequence divergence on diﬀerent chromosomes (sequence is largely non ­coding) 1.  What is the best explana7on for the diﬀerences in divergence on X and Y compared to autosomes?  ­Y chromosome occurs only in males, undergoes more replica&amp;ons per unit &amp;me. Thus, higher muta&amp;on rate per unit &amp;me compared to autosomes Male ­Biased Muta&amp;on  ­X chromosome occurs mostly in females (2/3 are in females in any one genera&amp;on), thus has a lower average muta&amp;on rate per unit &amp;me compared to autosomes. 2. How would you es7mate the muta7on rate from this average 1.2% divergence between chimps and humans? since K=u (subs&amp;tu&amp;on rate=muta&amp;on rate) divergence &amp;me=6 million years (fossils) human 0.012 changes/site/12 million years 6 Mya 1.2% 0.001 subs&amp;&amp;ons/site/million year chimp NEUTRAL THEORY 9 Divergence time •  This equation might allow you to calculate divergence times between lineages more quickly : •  t = D/2u •  t = time since divergence from a common ancestor •  D = number of base pair differences between two sequences. •  u = neutral mutation rate Human ­chimp sequence divergence on diﬀerent chromosomes (sequence is largely non ­coding) 2. How would you es7mate the divergence 7me given a 0.001 subs7tu7ons/site/ million years and average 1.2% divergence between...
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