Keystone Test Biology: Genetics and Evolution 3 — Questions and Answers
Question 1: What is the role of RNA polymerase during transcription?
- Unwinds DNA and synthesizes an mRNA strand (Correct answer)
- Translates mRNA into protein
- Replicates DNA before cell division
- Splices introns from pre-mRNA
Correct answer: Unwinds DNA and synthesizes an mRNA strand
RNA polymerase reads the DNA template strand and synthesizes a complementary mRNA molecule.
Question 2: Hardy-Weinberg equilibrium requires which of the following conditions?
- Strong directional selection
- No gene flow between populations (Correct answer)
- Small population size
- High mutation rate
Correct answer: No gene flow between populations
Hardy-Weinberg equilibrium requires no gene flow, no mutation, random mating, large population size, and no selection.
Question 3: Which term describes the evolutionary process by which two species each evolve in response to changes in the other?
- Convergent evolution
- Coevolution (Correct answer)
- Adaptive radiation
- Allopatric speciation
Correct answer: Coevolution
Coevolution occurs when two or more species reciprocally affect each other's evolution, as in predator-prey or host-parasite relationships.
Question 4: A DNA strand reads 3'-TACGGA-5'. What is the complementary mRNA sequence?
- 5'-AUGCCU-3' (Correct answer)
- 3'-AUGCCU-5'
- 5'-UACGGA-3'
- 3'-TACGGA-5'
Correct answer: 5'-AUGCCU-3'
mRNA is synthesized antiparallel to the DNA template, replacing thymine (T) with uracil (U): 3'-TACGGA-5' → 5'-AUGCCU-3'.
Question 5: What type of chromosomal mutation results in a segment being transferred to a non-homologous chromosome?
- Inversion
- Duplication
- Deletion
- Translocation (Correct answer)
Correct answer: Translocation
Translocation moves a chromosomal segment to a different, non-homologous chromosome.
Question 6: Which observation by Darwin most directly supported his theory of descent with modification?
- Similarities among Galapagos finch beaks adapted to different foods (Correct answer)
- The large size of Galapagos tortoises
- The presence of volcanoes on the Galapagos Islands
- The depth of water around the islands
Correct answer: Similarities among Galapagos finch beaks adapted to different foods
The varied beak shapes of Galapagos finches suggested they descended from a common ancestor and adapted to different food sources.
Question 7: A person is heterozygous for a recessive lethal allele (Aa). What is the probability that two such parents produce a surviving offspring with the lethal genotype?
- 0% — they cannot survive (Correct answer)
- 25%
- 50%
- 75%
Correct answer: 0% — they cannot survive
The aa genotype is lethal, so although 1/4 of conceptions are aa, none survive, and the question asks for surviving offspring with that genotype.
Keystone Test Biology: Genetics and Evolution 3
What is the role of RNA polymerase during transcription?