Answer :
The scenario described is an example related to plant and animal breeding, specifically in genetics concerning the formation of F1 and F2 offspring from two different species.
Understanding the Terms:
- Species H and Species S are two related species whose chromosomes have diverged in such a way that they cannot pair up during meiosis. Here, 'n' represents the number of chromosomes in the gametes; species H has [tex]n=13[/tex] and species S has [tex]n=9[/tex].
F1 and F2 Generations:
- The F1 generation is the first generation of offspring resulting from a cross between two different species or genetic lines. These F1 individuals are typically sterile because their chromosomes cannot form homologous pairs during meiosis.
- Occasionally, however, viable and fertile F2 generations (second filial generation) can arise.
Concept of Allopolyploidy:
- The rare fertile F2 offspring mentioned in the scenario demonstrate a concept known as allopolyploidy. This occurs when two different species with distinct sets of chromosomes produce a hybrid, which then undergoes chromosome doubling, resulting in a new, stable species with multiple sets of chromosomes from more than one species.
- Allopolyploid species can be fertile because the doubled chromosome sets allow pairing during meiosis, overcoming the initial sterility issue seen in the F1 generation.
Why This is Not Other Options:
- Autopolyploidy refers to chromosome doubling within a single species, not between species as in this scenario.
- Monoploidy (having a single set of chromosomes) and monosomy (having one chromosome from a pair missing) are not relevant to the formation of fertile hybrids.
- Trisomy involves the presence of an extra chromosome, which is not related to the fertility in this specific context.
The correct multiple-choice option is b. Allopolyploidy.
This scenario illustrates the importance of chromosome behavior in hybrid species and contributes valuable insights into the mechanisms of speciation and hybrid vigor.
