A male African clawed frog (Xenopus laevis) and a female Western clawed frog (Xenopus tropicalis) mate and produce multiple hybrid embryos that die early in development. Given this, death of the hybrid embryo is most likely caused by:

Question

A male African clawed frog (Xenopus laevis) and a female Western clawed frog (Xenopus tropicalis) mate and produce multiple hybrid embryos that die early in development.  Given this, death of the hybrid embryo is most likely caused by:

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11ecba2d_102a_3997_a3bf_815a6c6111cf_MD0008_00 Hybrid offspring are produced when members of two different species interbreed. The mating of hybrid offspring with members of either parental species may cause genetic leakage, or the transfer of genetic information between species. However, in some cases, two species may be unable to produce hybrid embryos or hybrids may be inviable (unable to survive) or infertile. The inability of two species to produce viable or fertile hybrid offspring is called reproductive isolation, which may be prezygotic (before zygote formation) or postzygotic (after zygote formation). In this scenario, mating of a male African clawed frog (Xenopus laevis) and a female Western clawed frog (Xenopus tropicalis) produces hybrid embryos that die early in development, making this an example of postzygotic reproductive isolation. Mitosis is essential for embryonic growth and production of the organism's somatic cells. Failure of sister chromatids to segregate properly (eg, due to chromosomal nondisjunction) during embryonic mitosis would generate cells containing missing or extra genetic information. Accordingly, the ability of these cells to divide and differentiate into functional somatic cells in the embryo would be impaired. This would inhibit zygote development and likely cause early embryonic death. (Choice B) Sperm and egg incompatibility in the two species would prevent fertilization and the formation of an embryo. Because mating of these frog species produced embryos, the sperm and egg must be compatible. (Choice C) Gametes (eggs, sperm) form via meiosis during gametogenesis. Reduced sperm and egg production in parental species would decrease the probability of fertilization and zygote formation following a mating event. However, the frogs are described as having produced multiple hybrid embryos, and reduced gamete formation in the parental species would not affect the development of any embryos formed after mating. (Choice D) During meiosis I, homologous chromosomes pair up and are segregated into cells that divide to form gametes in meiosis II. This process ensures the production of viable gametes containing correct chromosomal numbers. Errors in this process would impair gametogenesis in the hybrid offspring and potentially lead to infertility. However, impaired gametogenesis in the hybrid offspring would not cause embryonic death. Educational objective: Hybrid offspring are produced from the mating of two different species. However, reproductive isolation (prezygotic or postzygotic) may prevent different species from producing viable or fertile hybrid offspring.

A Male African Clawed Frog (Xenopus Laevis) and a Female