Normal nonrecombinant gamete

-Nonviable recombinant gametes

Nonrecombinant gamete with pericentric inversion

Conclusion: Recombinant gametes are nonviable because genes are missing or present in too many copies.

9.14 In a heterozygous individual, a single crossover within a pericentric inversion leads to abnormal gametes.

double crossovers), result in functional, recombinant chromosomes. (Try drawing out the results of a double crossover.) Thus, even though the overall rate of recombination is reduced within an inversion, some viable recombinant progeny may still be produced through two-stranded double crossovers.

Inversion heterozygotes are common in many organisms, including a number of plants, some species of Drosophila, mosquitoes, and grasshoppers. Inversions may have played an important role in human evolution: G-banding patterns reveal that several human chromosomes differ from those of chimpanzees by only a pericen-tric inversion ( FIGURE 9.15).

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