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wk9ans - Covel Peer Learning LS 4(Rachel Care Week 9 Week...

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Covel Peer Learning – LS 4 (Rachel Care) Week 9 Week 8/9 Material: I. Positional Cloning purpose: to identify disease loci; to aid in disease prediction “RFLP” stands for: Restriction Fragment Length Polymorphism RFLPs are visualized by: restriction endonucleases, whose cleavage sites are disrupted by the molecular marker. The endonuclease treated DNA is run on a gel and the different lengths of the bands indicates the presence or absence of the cleavage site and this the molecular marker. 1. A rare recessive X-linked mutation, d, has been found which is caused by a point mutation (single nucleotide polymorphism) in exon 1 of the gene responsible for particularly bad dancing. The mutation happens to cause a RFLP such that EcoRI will not cut the mutant fragment. EcoRI normally cute to give two bands: 200 bp and 600 bp. Assume that unrelated individuals do not carry the mutation. Fill in genotypes for known individuals and possible genotypes for the unknowns: 1 2 3 4 5 6 7 8 9 Genotype Dd DY DY Dd DY DD dY dY DD (s) Dd Dd Draw the appropriate bands on the gel for each individual: Ladder 1 2 3 4 5 6 7 8 9 ( ) ( ) 2. A witch has 9 children and wants to know which of them will grow up to
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develop magic powers. The ability to perform magic is caused by a dominant mutation in the boredom gene. The witch marries a wizard, but both are half-bloods (ie, each had one Muggle parent). The witch comes to UCLA seeking genetic counseling to see which of her 9 children are Squibs (are non-magical). You find a single nucleotide polymorphism 20cM away from the boredom gene that causes a RFLP. By genotyping the grandparents, you know that the allele of the RFLP that doesn’t get cut is linked to the B allele in both the witch and wizard. a. Given kid 1’s RFLP genotype, what is the probability she’s BB? At first glance we think she’d be BB because she only has the RFLP that is linked to the B allele. But because the molecular marker is 20 cM away from the gene, there is a 20% chance that recombination could happen between them and then the RFLP would not actually predict the allele at the boredom gene. Chances of NO interrupting recombinations: 0.8. she’s got two chromosomes, so 0.8 x 0.8 = 0.64 b. Given kid 2’s RFLP genotype, what is the probability she’s BB? To be BB kid 2 would have had to have had TWO recombinations between the RFLP and
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wk9ans - Covel Peer Learning LS 4(Rachel Care Week 9 Week...

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