BIOC15H3 Lecture Notes - Lecture 11: Ichthyosis, Polytene Chromosome, Vulgate
18 Nov 2013
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Bioc15fall2013 lecture 11 notes: genetic mapping and mutations. Problem: ichthyosis: the xg locus on the x-chromosome has two alleles xg a+ and xg a (let"s call them + normal and a lacking antigen). The xg locus is about 10 map units away from the x-linked ichthyosis (sts) locus. A man with x-linked ichthyosis (scaly skin) and no xg antigen has a normal daughter with xg antigen who marries a man normal skin and no xg antigen. In the parents, you always have vg an b together and vg+ b+ together which is mainting in these double crossovers. Which means that the middle gene must then be pr. X pr: and f1 is pr vg. / pr vg crossed to the tester males. Interference the phenomenon in which the presence of one crossover interferes with the formation of a crossover nearby. Interference = 1-coefficient of coincidence: coefficient of coincidence = observed double crossover freq.
