Introduction to Genetic Analysis 506

Introduction to - 44200_15_p481-520 1:07 PM Page 505 15.2 Changes in chromosome structure 505 Cri du chat syndrome 15.3 15.2 15.1 p 1 14 13 12 11

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duplication (not found) and a Williams syndrome dele- tion, as shown in Figure 15- 31. Most human deletions, such as those that we have just considered, arise spontaneously in the gonads of a normal parent of an affected person; thus usually no signs of the deletions are found in the chromosomes of the parents. Less commonly, deletion-bearing individuals appear among the offspring of an individual having an undetected balanced rearrangement of chromosomes. For example, cri du chat syndrome can result from a par- ent heterozygous for a reciprocal translocation, because adjacent segregation produces deletions. Recombination within a pericentric inversion heterozygote also pro- duces deletions. Animals and plants show differences in the survival of gametes or offspring that bear deletions. A male animal with a deletion in one chromosome pro- duces sperm carrying one or the other of the two chro- mosomes in approximately equal numbers. These sperm seem to function to some extent regardless of their ge- netic content. In diploid plants, on the other hand, the
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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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