Introduction to Genetic Analysis 47

Introduction to Genetic Analysis 47 - 44200_02_p27-72...

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46 Chapter 2 Patterns of Inheritance However, it is a late-onset disease, the symptoms gener- ally not appearing until after the person has begun to have children (Figure 2-17). Each child of a carrier of the abnormal allele stands a 50 percent chance of inheriting the allele and the associated disease. This tragic pattern has inspired a great effort to find ways of identifying peo- ple who carry the abnormal allele before they experience the onset of the disease. The application of molecular techniques has resulted in useful screening procedures. Some other rare dominant conditions are poly- dactyly (extra digits), shown in Figure 2-18, and piebald spotting, shown in Figure 2-19. I II III 1 1234567891 0 1 11 2 1 3 A/a a/a 23 4 5 6 7 1 2 a/aa/aa/aa/aA/aa/aA/aa/aa/aa/aA/aa/aA/a Of all persons carrying the allelle, percentage affected with the disease 0 10 20 30 40 50 60 70 80 50 100 Age (years) Figure 2-16 Pedigree of a dominant phenotype determined by a dominant allele A . In this pedigree, all the genotypes have been deduced.
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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