BIOD 210 Genetics Final Exam Questions
and Answers () (Verified Answers)
In a monohybrid cross between two heterozygous pea plants (Tt × Tt), what proportion
of the F1 generation is expected to be homozygous recessive?
A. 1/4
B. 1/2
C. 3/4
D. 1/8
Correct Answer: A
Rationale: A standard Punnett square of Tt × Tt yields 1 TT : 2 Tt : 1 tt; thus 1/4 of
offspring are homozygous recessive (tt).
In snapdragons, red (CRCR) crossed with white (CWCW) produces pink (CRCW) F1
progeny. This is an example of:
A. complete dominance
B. incomplete dominance
C. codominance
D. epistasis
Correct Answer: B
Rationale: Incomplete dominance produces an intermediate heterozygous phenotype
(pink) between the two parental extremes.
A man with type A blood (genotype IAi) marries a woman with type B blood (IBi). What
is the probability their first child has type O blood?
A. 0%
B. 25%
C. 50%
D. 75%
Correct Answer: B
,Rationale: Both parents are heterozygous (IAi × IBi); 1/4 of offspring inherit ii (type O).
In humans, red-green color blindness is X-linked recessive. A color-blind man and a
carrier woman produce a son. The probability the son is color-blind is:
A. 0%
B. 25%
C. 50%
D. 100%
Correct Answer: C
Rationale: Sons inherit the X chromosome from the mother; a carrier female (XCXc)
passes Xc to half her sons, who are therefore color-blind.
A pedigree shows affected males in every generation with no affected females. The
most likely mode of inheritance is:
A. autosomal dominant
B. autosomal recessive
C. X-linked recessive
D. mitochondrial
Correct Answer: C
Rationale: X-linked recessive traits appear predominantly in males and are transmitted
through carrier females; absence of affected females supports this.
DNA replication in eukaryotes begins at specific sites called:
A. telomeres
B. origins of replication
C. promoters
D. centromeres
Correct Answer: B
Rationale: Origins of replication are short DNA sequences recognized by initiation
proteins where bidirectional replication starts.
, The 5’ → 3’ exonuclease activity of DNA polymerase I in prokaryotes is primarily
involved in:
A. adding nucleotides to the 3’ end
B. proofreading newly synthesized DNA
C. removing RNA primers
D. joining Okazaki fragments
Correct Answer: C
Rationale: DNA polymerase I uses its 5’ → 3’ exonuclease activity to excise RNA
primers and replace them with DNA during lagging-strand synthesis.
Which enzyme is responsible for joining Okazaki fragments on the lagging strand?
A. DNA polymerase III
B. primase
C. DNA ligase
D. helicase
Correct Answer: C
Rationale: DNA ligase seals nicks between adjacent DNA fragments by forming
phosphodiester bonds, completing lagging-strand synthesis.
Telomerase maintains chromosome ends by:
A. adding histone proteins
B. synthesizing RNA primers
C. extending the 3’ overhang of telomeres
D. sealing telomere loops
Correct Answer: C
Rationale: Telomerase is a reverse transcriptase that uses its RNA template to add
repetitive DNA sequences to the 3’ overhang, counteracting shortening.
The Meselson-Stahl experiment demonstrated that DNA replication is:
A. conservative
and Answers () (Verified Answers)
In a monohybrid cross between two heterozygous pea plants (Tt × Tt), what proportion
of the F1 generation is expected to be homozygous recessive?
A. 1/4
B. 1/2
C. 3/4
D. 1/8
Correct Answer: A
Rationale: A standard Punnett square of Tt × Tt yields 1 TT : 2 Tt : 1 tt; thus 1/4 of
offspring are homozygous recessive (tt).
In snapdragons, red (CRCR) crossed with white (CWCW) produces pink (CRCW) F1
progeny. This is an example of:
A. complete dominance
B. incomplete dominance
C. codominance
D. epistasis
Correct Answer: B
Rationale: Incomplete dominance produces an intermediate heterozygous phenotype
(pink) between the two parental extremes.
A man with type A blood (genotype IAi) marries a woman with type B blood (IBi). What
is the probability their first child has type O blood?
A. 0%
B. 25%
C. 50%
D. 75%
Correct Answer: B
,Rationale: Both parents are heterozygous (IAi × IBi); 1/4 of offspring inherit ii (type O).
In humans, red-green color blindness is X-linked recessive. A color-blind man and a
carrier woman produce a son. The probability the son is color-blind is:
A. 0%
B. 25%
C. 50%
D. 100%
Correct Answer: C
Rationale: Sons inherit the X chromosome from the mother; a carrier female (XCXc)
passes Xc to half her sons, who are therefore color-blind.
A pedigree shows affected males in every generation with no affected females. The
most likely mode of inheritance is:
A. autosomal dominant
B. autosomal recessive
C. X-linked recessive
D. mitochondrial
Correct Answer: C
Rationale: X-linked recessive traits appear predominantly in males and are transmitted
through carrier females; absence of affected females supports this.
DNA replication in eukaryotes begins at specific sites called:
A. telomeres
B. origins of replication
C. promoters
D. centromeres
Correct Answer: B
Rationale: Origins of replication are short DNA sequences recognized by initiation
proteins where bidirectional replication starts.
, The 5’ → 3’ exonuclease activity of DNA polymerase I in prokaryotes is primarily
involved in:
A. adding nucleotides to the 3’ end
B. proofreading newly synthesized DNA
C. removing RNA primers
D. joining Okazaki fragments
Correct Answer: C
Rationale: DNA polymerase I uses its 5’ → 3’ exonuclease activity to excise RNA
primers and replace them with DNA during lagging-strand synthesis.
Which enzyme is responsible for joining Okazaki fragments on the lagging strand?
A. DNA polymerase III
B. primase
C. DNA ligase
D. helicase
Correct Answer: C
Rationale: DNA ligase seals nicks between adjacent DNA fragments by forming
phosphodiester bonds, completing lagging-strand synthesis.
Telomerase maintains chromosome ends by:
A. adding histone proteins
B. synthesizing RNA primers
C. extending the 3’ overhang of telomeres
D. sealing telomere loops
Correct Answer: C
Rationale: Telomerase is a reverse transcriptase that uses its RNA template to add
repetitive DNA sequences to the 3’ overhang, counteracting shortening.
The Meselson-Stahl experiment demonstrated that DNA replication is:
A. conservative
