Introduction to Genetic Analysis 120

Introduction to Genetic Analysis 120 - 44200_04_p115-150...

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119 4.1 The discovery of the inheritance patterns of linked genes New combinations of alleles arise from crossovers The linkage hypothesis explains why allele combina- tions from the parental generations remain together— because they are physically attached by the segment of chromosome between them. But how do we explain the appearance of the minority class of nonparental combi- nations? Morgan suggested that when homologous chro- mosomes pair in meiosis, the chromosomes occasionally break and exchange parts in a process called crossing- over. Figure 4-3 illustrates this physical exchange of chromosome segments. The two new combinations are called crossover products. Evidence that crossing-over is a breakage-and-rejoining process The idea that recombinants were produced by some kind of exchange of material between homologous chro- mosomes was a compelling one. But experimentation was necessary to test this hypothesis. One of the first pr vg + + + + + + Parental chromosomes
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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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