Genetic variation Original Scenario-Based Download PDF

Questions

1. 1.

   During an expedition to an isolated hydrothermal trench, marine biologists isolate an ember-fin crawler, a sexually reproducing diploid organism with two pairs of chromosomes ($2n = 4$). Genetic analysis of a single individual heterozygous for two unlinked traits ($AaBb$) demonstrates that even when crossing over is chemically inhibited, the organism produces four distinct gametic genotypes—$AB$, $Ab$, $aB$, and $ab$—in equal proportions. Which meiotic process directly accounts for the generation of these diverse allele combinations in the gametes?

   • A) Random fusion of gametes during external fertilization in the aquatic environment
   • B) Symmetrical exchange of sister chromatids during mitotic anaphase
   • C) Alternative splicing of precursor messenger RNA molecules during interkinesis
   • D) Independent orientation and separation of homologous chromosome pairs during meiosis I