lecture27

lecture27 - Lecture 27 Effects of Inbreeding: Today we will...

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Lecture 27 Effects of Inbreeding: Today we will examine how inbreeding between close relatives (also known as consanguineous matings) influences the appearance of autosomal recessive traits. Note that inbreeding will not make a difference for dominant traits because they need only be inherited from one parent or for X-linked traits since they are inherited from the mother. Consider an extreme case of inbreeding namely a brother-sister mating. ? A useful concept is the Inbreeding Coefficient = F which is defined as the likelihood of homozygosity by descent at a given locus. If we consider a locus with different alleles in each grandparent: A1 , A2 , A3 , A4 , F is the probability that the grandchild will be either A1 / A1 , A2 / A2 , A3 / A3 , A4 / A4 p( A1 / A1 ) = 1 / 2 . 1 / 2 . 1 / 4 = 1 / 16 " p( A2 / A2 ) = = 1 / 16 " p( A3 / A3 ) = = 1 / 16 " p( A4 / A4 ) = = 1 / 16 p(homozygous by descent) = 4 . 1 / 16 F = 1 / 4 A bother-sister mating is the simplest case but is of little practical consequence in human population genetics since all cultures have strong taboos against this type of consanguineous mating and the frequency is extremely low.
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This note was uploaded on 09/03/2009 for the course BIOL 7.03 taught by Professor Chriskaiser during the Fall '04 term at MIT.

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lecture27 - Lecture 27 Effects of Inbreeding: Today we will...

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