Keystone Test Biology: Genetics and Evolution 5

Question 1

A point mutation changes a codon from UAC (Tyrosine) to UAA (Stop). This is classified as a:

Accepted Answer

Nonsense mutation

Answer

A nonsense mutation changes an amino acid codon into a premature stop codon, truncating the resulting protein.

Question 2

Two species of birds live in the same area but mate at different times of year, preventing interbreeding. This is an example of:

Accepted Answer

Temporal isolation

Answer

Temporal isolation is a prezygotic barrier where species breed at different times (seasons, times of day) and thus never interbreed.

Question 3

In a population where p = 0.3 (dominant allele), what is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium?

Accepted Answer

0.42

Answer

Heterozygote frequency = 2pq = 2(0.3)(0.7) = 0.42 under Hardy-Weinberg equilibrium.

Question 4

Which cellular process produces gametes with half the chromosome number of the parent cell?

Accepted Answer

Meiosis

Answer

Meiosis reduces the chromosome number by half through two successive divisions, producing haploid gametes.

Question 5

Analogous structures in unrelated species (e.g., wings of bats and insects) are evidence of:

Accepted Answer

Convergent evolution

Answer

Analogous structures arise independently in unrelated lineages that face similar environmental pressures, demonstrating convergent evolution.

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