CLEP Biology Genetics & Biological Diversity 2 — Questions and Answers
Question 1: In a dihybrid cross between two organisms heterozygous for both traits (AaBb × AaBb), what fraction of offspring will express both dominant phenotypes?
- 1/16
- 3/16
- 9/16 (Correct answer)
- 12/16
Correct answer: 9/16
The 9:3:3:1 ratio means 9/16 offspring express both dominant phenotypes.
Question 2: Which of the following best describes incomplete dominance?
- One allele completely masks the other
- Both alleles are expressed simultaneously
- The heterozygote shows a blended intermediate phenotype (Correct answer)
- One allele is expressed only in males
Correct answer: The heterozygote shows a blended intermediate phenotype
In incomplete dominance, the heterozygote phenotype is intermediate between the two homozygous phenotypes (e.g., red × white = pink).
Question 3: A bacterium that can synthesize all needed amino acids is best described as a:
- Heterotroph
- Auxotroph
- Prototroph (Correct answer)
- Saprotroph
Correct answer: Prototroph
A prototroph is a wild-type microorganism capable of synthesizing all required organic compounds from inorganic precursors.
Question 4: Which domain includes organisms with peptidoglycan in their cell walls and no membrane-bound nucleus?
- Eukarya
- Archaea
- Bacteria (Correct answer)
- Protista
Correct answer: Bacteria
Bacteria have cell walls containing peptidoglycan and lack a membrane-bound nucleus.
Question 5: During meiosis, genetic variation is increased by crossing over, which occurs during:
- Metaphase I
- Prophase I (Correct answer)
- Anaphase II
- Telophase II
Correct answer: Prophase I
Crossing over (recombination) between homologous chromosomes occurs during Prophase I of meiosis.
Question 6: The biological species concept defines a species primarily by:
- Morphological similarity
- Genetic sequence identity
- Reproductive isolation (Correct answer)
- Geographic distribution
Correct answer: Reproductive isolation
The biological species concept defines a species as a group of populations whose members can interbreed and produce fertile offspring, separated from other groups by reproductive isolation.
Question 7: Which type of RNA carries amino acids to the ribosome during translation?
- mRNA
- rRNA
- tRNA (Correct answer)
- snRNA
Correct answer: tRNA
Transfer RNA (tRNA) carries specific amino acids to the ribosome, where it base-pairs with the mRNA codon via its anticodon.
CLEP Biology Genetics & Biological Diversity 2
In a dihybrid cross between two organisms heterozygous for both traits (AaBb × AaBb), what fraction of offspring will express both dominant phenotypes?