[Campbell Biology P.1091] A female Komodo dragon kept in isolation produced offspring, each w... | Practice Question

A female Komodo dragon kept in isolation produced offspring, each with two identical copies of every gene, yet the offspring were not genetically identical to each other. Which hypothesis best explains these observations based on parthenogenesis and meiosis?

  • A: The offspring resulted from diploid eggs formed without meiosis, and subsequent mutations caused variation.
  • B: The female produced diploid eggs through a modified meiosis II, where the second polar body fused with the ovum, and crossing over during meiosis I led to variation.
  • C: The offspring were clones produced by mitosis, and epigenetic changes caused the observed differences.
  • D: Fertilization occurred externally, and the mother accidentally consumed the male's sperm.

Explanation

Komodo dragon parthenogenesis often occurs via automixis, specifically a mechanism where a diploid egg is formed by the fusion of a secondary oocyte and its second polar body. Meiosis I, which includes crossing over, still occurs, creating genetic variation in the alleles passed to the secondary oocyte. When the second polar body fuses with the ovum, it restores diploidy, resulting in offspring that are largely homozygous explaining 'two identical copies of every gene' at many loci but are genetically distinct from each other due to the recombination events in Meiosis I.