Introduction to Genetic Analysis 493

Introduction to Genetic Analysis 493 - 44200_15_p481-520...

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492 Chapter 15 Large-Scale Chromosomal Changes XO. Affected persons have a characteristic phenotype: they are sterile females, short in stature, and often have a web of skin extending between the neck and shoul- ders (Figure 15-14). Although their intelligence is near normal, some of their speci±c cognitive functions are defective. About 1 in 5000 female births show Turner syndrome. Geneticists have used viable plant monosomics to match newly discovered recessive mutant alleles to a speci±c chromosome. For example, one can make a set of monosomic lines, each known to lack a different chro- mosome. Homozygotes for the new mutant allele are crossed with each monosomic line, and the progeny of each cross are inspected for the recessive phenotype. The appearance of the recessive phenotype identi±es the chromosome that has one copy missing as the one the gene is normally located on. The test works because half the gametes of a fertile monosomic will be n 2 1, and when an n 2 1 gamete is fertilized by a gamete bearing
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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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