Molecular evidence Knowledge-Based Practice

Questions

1. 1.

   Why does finding an identical endogenous retrovirus (ERV) sequence at the exact same genomic locus in two distinct species provide strong evidence of common ancestry?

   • A) Retroviruses selectively target predetermined nucleotide sequences that are naturally conserved across all mammals.
   • B) ERV sequences represent essential functional genes that are actively maintained by stabilizing selection across diverse species.
   • C) The probability of independent viral integration into the exact same genomic position in two separate lineages is extraordinarily low, indicating the insertion occurred in their shared ancestor prior to divergence.
   • D) Retroviral integrations consistently occur immediately downstream of active promoter regions during periods of intense environmental stress.
2. 2.

   Which underlying principle enables scientists to use molecular clocks to estimate the time of divergence between two evolutionary lineages?

   • A) Neutral mutations accumulate at a relatively constant rate over evolutionary time.
   • B) Natural selection actively preserves beneficial mutations at a fixed, uniform rate across all lineages.
   • C) Deleterious mutations become permanently fixed in protein-coding genes at a predictable frequency.
   • D) Environmental stress causes mutation rates to remain strictly synchronized among unrelated organisms.
3. 3.

   How do pseudogenes provide molecular evidence supporting common ancestry among distinct species?

   • A) Shared identical inactivating mutations in non-functional gene copies reflect inheritance from a shared ancestor.
   • B) Independent functional mutations arise spontaneously in identical loci across unrelated organisms to meet environmental demands.
   • C) Active non-coding sequences systematically mutate to restore lost metabolic pathways during speciation events.
   • D) Universal DNA repair templates prevent genetic divergence by preserving identical protein structures across kingdoms.
4. 4.

   When comparing the amino acid sequences of cytochrome c among different vertebrate species, what pattern indicates a more recent common ancestor between two organisms?

   • A) A greater total number of amino acid differences throughout the protein chain
   • B) A smaller number of amino acid differences in the polypeptide sequence
   • C) An identical sequence of non-coding introns flanking the functional gene
   • D) A complete absence of identical functional domains within the folded enzyme
5. 5.

   Which of the following provides direct molecular evidence supporting the hypothesis that all living organisms share a universal common ancestor?

   • A) The nearly universal genetic code and shared nucleic acid building blocks found across all domains of life
   • B) The structural similarities found in the homologous forelimbs of humans, whales, and bats
   • C) The presence of transitional fossil forms preserved within sequential sedimentary rock strata
   • D) The convergent evolution of streamlined body shapes in sharks and dolphins inhabiting marine environments

Answers and step-by-step solutions appear after you finish the test.