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Lecture 12

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University of Toronto St. George
John Stinchcombe

BIO220 Lecture 12  Genome Transmission: different parts of the genome have alternative modes of transmission (comes from only one parent ex. mitochondria  maternally inherited)  Show can we use this data on genome? o We can use regions of the genome that are inherited from both parents to see what both parents have contributed to? o So we can use genetic markers to understand the evolutionary process and we can use our understanding to make sense of the patterns we see Example: Elephants  Groups are composed of females and juveniles. Males are kicked out at puberty  Can males recognize their sisters, and mothers when they reassociate with females  So can they avoid mating with their sisters and mothers?  Problem: male elephants can keep reproducing for a long time because of their long lifespan. So they can also encounter their own daughters :o  Prediction 1: Elephants have evolved inbreeding avoidance because inbreeding depression is severe o Inbreeding depression  loss of fitness because the consequence of mating with relatives are so severe  Prediction 2: Natural selection has NOT led to inbreeding avoidance because inbreeding depression is weak (there is no cost) and/or male reproductive success is so highly variable (ex. male elephants fight, and the elephant that wins these fights reproduces a lot. The elephant that loses doesn’t mate. So if your chances of mating is 0% then take the risk and mate with relatives because the alternative is not mating at all)  Experiment: Use genetic markers because can’t do experiments with elephants (their life span is too long). Observe elephant behaviour and watch who mates with who and try to assess whether they’re mating with their own relatives. You can determine mother because baby and mom interactions but harder to determine father. So you gather elephant poo, extract DNA and do a paternity test :p Results: Below the X-axis is behaviour towards close kin, and above axis is behaviour towards non-natal family. So the elephants are directing their courtship behaviour, number of copulations and having more offspring with individuals they are not closely related to. This is not just male elephants avoiding their sisters, mothers and daughters, but also male elephants avoiding their half sisters (from father’s side) Conclusion: Inbreeding depression is really significant in elephants. That the cost of mating with relatives is worse than not mating at all There’s a strong possibility that a female is asserting some choice when choosing mate. Example: Wolf Populations in Canada  Some migrate, others don’t, so why is this the case? Are these wolves different ecotypes? What ecological forces lead to migration differences?  Questions: Is there gene flow between northern, migratory wolves and southern resident wolves? Is there evidence of differentiation between northern and southern wolves?  Experiment: Study wolves; take blood samples, traps to get hair (follicles) DNA. They extracted DNA’s and sampled alleles and watched if they all clustered (did DNA from North al cluste
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