ANSC 313 Lecture Notes - Lecture 21: White Park Cattle, Jersey Cattle, Genetic Drift
equilibrium with unequal q for each sex:!
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Genetic drift!
small subpopulations become increasingly different over generations!
i.e polydactyly " common" in maritimes cats!•
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population size influences the chance of "drift"!•
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founder effect!
founding small population (herd) is not randomly selected from the total population!•
gene frequency changed are due to chance!•
founder effect is not nessisarily by chance!•
example: C.D.I. in Arabians (combined immunodeficiency)!
$- autosomal recessive disease!
$- in england the q ~0.1!
$- only about 1% has CID in Arabians!
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Breed introduction!
"exotic" cattle to canada!•
holsteins to kenya!•
llamas to california!•
typically a relatively small number of animals " found" the population!
"new" population could be very different from parent population in terms of gene frequency!
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"closed" herd!
swine companies!•
example: N.P.D.!•
because they do not introduce new animals they just breed wishing the herd!•
closed to outside genetics!•
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Population bottleneck!
population is severely reduced in numbers for 1 or more generations!•
can cause genetic drift!◦
examples:!•
jersey cattle in saskatchewan!◦
white park cattle in england!◦
Ridley bronze turkeys!◦
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Show ring & A.I.!
promotes "few" select sires!•
these are used extensively!•
tend to promote very few select sires!◦
used disproportionately!◦
can cause genetic problems if he is a carrier for something: giving an outbreak of the ◦
genetic problem!
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Gene Flow!
recurrent exchange of new alleles between subpopulations!•
