The African clawed frog (Xenopus laevis) is allotetraploid, likely as a result of an interspecies mating long ago, followed by a duplication of the entire genome. Xenopus laevis is fertile and has a normal life cycle. In contrast, mules, the allodiploid offspring of a male donkey and a female horse, are generally sterile. Why can Xenopus reproduce and mules cannot?
A) Frogs are less sensitive to multiple copies of the genome than mammals.
B) In allotetraploid organisms each chromosome has a chromosome to pair up with in meiosis, whereas in allodiploid organisms they do not.
C) The two frogs that interbred to form the Xenopus laevis must have been more closely genetically related than the donkey and horse are.
D) The mule must have a genetic mutation that prevents it from reproducing.

Question

Quizplus · Accepted Answer

Allotetraploid organisms have two sets of chromosomes from each parent species, which can pair up during meiosis. In contrast, allodiploid organisms have only one set of chromosomes from each parent species, which cannot pair up properly during meiosis. This often results in gametes with unpaired chromosomes, making it difficult or impossible for the organism to reproduce. In the case of Xenopus laevis, each of its four sets of chromosomes can pair up with another set during meiosis, allowing it to reproduce normally.

The African Clawed Frog (Xenopus Laevis) Is Allotetraploid, Likely as a Result