Molecular evidence Knowledge-Based Download PDF

Questions

1. 1.

   In DNA-DNA hybridization studies used to assess evolutionary relationships, which observation indicates that two species share a more recent common ancestor?

   • A) A lower melting temperature ($T_m$) required to separate the hybrid double-stranded DNA molecules
   • B) A complete failure of single-stranded DNA from the two species to form base-paired hybrid duplexes
   • C) A higher melting temperature ($T_m$) required to separate the hybrid double-stranded DNA molecules
   • D) A greater number of mismatched base pairs remaining bonded at elevated temperatures
2. 2.

   Which statement best describes the fundamental principle underlying the use of a molecular clock in evolutionary biology?

   • A) It relies on tracking how quickly adaptive phenotypes become fixed within a population under intense natural selection.
   • B) It measures the progressive physical loss and degradation of cellular RNA molecules across successive generations.
   • C) It calculates the rate of radioactive isotope decay trapped within fossilized segments of ancient genomic DNA.
   • D) It assumes that neutral nucleotide mutations accumulate in homologous genomic regions at a relatively constant rate over evolutionary time.
3. 3.

   How does the presence of shared pseudogenes among different species provide molecular evidence for common ancestry?

   • A) Shared pseudogenes with identical disabling mutations in related species suggest inheritance from a common ancestor.
   • B) Pseudogenes produce alternate forms of essential metabolic enzymes that confer novel adaptive advantages.
   • C) Pseudogenes prevent point mutations in adjacent coding sequences to preserve ancestral DNA structures.
   • D) Shared pseudogenes demonstrate that organisms have independently evolved identical functional adaptations through convergent evolution.
4. 4.

   When comparing the amino acid sequence of a homologous protein such as cytochrome c across different organisms, which observation indicates that two species shared a common ancestor most recently?

   • A) Having the fewest differences in their amino acid sequences
   • B) Having the greatest number of amino acid substitutions
   • C) Possessing identical codon sequences across all cellular proteins
   • D) Lacking any silent mutations in the gene encoding the protein
5. 5.

   Which of the following observations provides the strongest molecular evidence that all living organisms share a common evolutionary ancestor?

   • A) The presence of homologous bone structures in the forelimbs of diverse vertebrates
   • B) The similar anatomical development observed during early embryonic stages of chordates
   • C) The near-universality of the genetic code used to translate nucleotide triplets into amino acids
   • D) The convergent evolution of streamlined body shapes in unrelated aquatic organisms