Biology Test Biology Genetics & Evolution 2 — Questions and Answers
Question 1: Which type of RNA carries amino acids to the ribosome during translation?
- mRNA
- tRNA (Correct answer)
- rRNA
- snRNA
Correct answer: tRNA
Transfer RNA (tRNA) carries specific amino acids to the ribosome, matching anticodons to mRNA codons.
Question 2: A cell has the genotype AaBb. If the two genes assort independently, what fraction of offspring from self-fertilization will be AABB?
- 1/4
- 1/16 (Correct answer)
- 1/8
- 3/16
Correct answer: 1/16
Each locus independently gives a 1/4 chance of AA, so the combined probability for AABB is 1/4 × 1/4 = 1/16.
Question 3: What is a frameshift mutation?
- A point mutation that changes one amino acid
- An insertion or deletion that alters the reading frame (Correct answer)
- A mutation that creates a premature stop codon
- A chromosomal inversion
Correct answer: An insertion or deletion that alters the reading frame
Frameshift mutations result from insertions or deletions of nucleotides that are not multiples of three, disrupting the reading frame.
Question 4: Natural selection acting on quantitative traits toward an intermediate phenotype is called:
- Directional selection
- Disruptive selection
- Stabilizing selection (Correct answer)
- Sexual selection
Correct answer: Stabilizing selection
Stabilizing selection favors intermediate phenotypes and reduces variation in a population over time.
Question 5: Which enzyme unwinds the DNA double helix during replication?
- DNA polymerase
- Ligase
- Helicase (Correct answer)
- Primase
Correct answer: Helicase
Helicase breaks hydrogen bonds between complementary base pairs to unwind the double helix at the replication fork.
Question 6: In incomplete dominance, two red snapdragons (RR) crossed with white snapdragons (WW) produce pink offspring. What is the phenotype ratio when two pink plants are crossed?
- All pink
- 1 red : 2 pink : 1 white (Correct answer)
- 3 pink : 1 white
- 1 red : 1 white
Correct answer: 1 red : 2 pink : 1 white
A cross between two pink (RW) plants yields RR : RW : WW in a 1:2:1 ratio, giving red, pink, and white phenotypes.
Question 7: Which of the following best describes allopatric speciation?
- Two populations speciate within the same geographic area
- A population becomes polyploid without geographic isolation
- Geographic isolation separates populations until they become reproductively isolated (Correct answer)
- Species diverge due to sexual selection only
Correct answer: Geographic isolation separates populations until they become reproductively isolated
Allopatric speciation occurs when geographic barriers physically separate populations, allowing them to diverge until reproductive isolation is complete.
Biology Test Biology Genetics & Evolution 2
Which type of RNA carries amino acids to the ribosome during translation?