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Modern Genetic Analysis Chapter 11. Applications of Recombinant DNA Technology
Solution

a. The probe detects three bands of 5, 3, and 2 kb. All family members have the 5-kb band. Five of the six affected persons have the 3- and 2-kb bands, but no unaffected persons have them; therefore, these fragments are likely to be linked in cis arrangement to the disease allele. Because 3 plus 2 adds up to 5, a likely arrangement in the father is as follows, where D is the disease allele and an arrowhead represents the restriction-enzyme target site:

The mother is as follows:

b. The last son most likely represents a crossover between the disease locus and the RFLP locus, resulting in a chromosome with D and the 5-kb fragment.
c. Because the 3- and 2-kb fragments are linked to the disease allele, the presence of these fragments can be used as a predictor for the disease. However, the diagnosis has to take into account the possibility of a crossover.
See question

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