lecture_18_notes

lecture_18_notes - Lecture 18 Mendelian genetics Mendel...

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Lecture 18 Mendelian genetics Mendel From previous lecture: finish testcross with dihybrid (two genes) Use of probability for complex problems According to Mendel's second law, Alleles of different genes assort independently: they thus follow under the product rule of probabilities Consider the following problem. A heterozygote has the genotype: AaBbCcDc. What is the probability that the first selfed progeny is AABBCCDD? There are four genes to account for. You know that for each gene the P of the big letter ho- mozygote is 1/4, i.e. P of AA from Aa self is 1/4 You can then solve this problem by multiplying the probabilities of each "per gene" genotype: 1/4x1/4x1/4x1/4 = 1/256 What is P of AABBCcDd from same het? 1/4x1/4x1/2x1/2 Cellular explanation for First and Second Law First law: paired chromosomes split at meiosis I. If not affected by crossing over, the two al- leles will split at anaphase I. If affected by crossing over, the two alleles split at anaphase II. Either way, they never enter the same gamete!
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lecture_18_notes - Lecture 18 Mendelian genetics Mendel...

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