Question

Now consider the following piece of information: at the Shedd Aquarium, Jaws
was the only male in the F1 generation at the time the shark pups were produced.
Based on this information and your answer to the previous question, what can
you conclude about how the F2 generation was produced? Provide evidence to
support your answer

Answer 1

Conclusion: the F2 pups were produced sexually by mating between the F1 individuals — specifically, Jaws (the only F1 male) sired the F2 by mating with F1 females (i.e., sibling inbreeding within the F1).

Evidence:
- Demography/timing: Jaws was the only male available in the F1 cohort at the time the pups were conceived, so any paternally contributed alleles in the pups must have come from him (no other F1 male could be the sire).
- Genetic signature: the pups carry alleles that are not present in their mothers but match Jaws’ genotype at multiple independent loci. That pattern cannot be produced by parthenogenesis (which in sharks produces offspring that inherit only maternal alleles and shows reduced heterozygosity/characteristic automictic signatures). The presence of paternal-only alleles and normal Mendelian segregation is strong direct evidence of sexual fertilization by Jaws.
- Observational/biological consistency: the pups’ genotype diversity and heterozygosity are inconsistent with the extreme homozygosity expected from parthenogenetic offspring, and the timing of pregnancies is compatible with mating having occurred while Jaws was the sole male.

Together these points show the F2s were produced sexually and that Jaws was the sire.