BIOD 210 MODULE 2 EXAM 2026/2027 | Genetics | Latest
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Q1: In a monohybrid cross between two heterozygous tall pea plants (Tt × Tt), what is
the expected phenotypic ratio in the offspring?
A. 1 tall : 1 short
B. 3 tall : 1 short [CORRECT]
C. 1 tall : 2 intermediate : 1 short
D. All tall
Correct Answer: B
Rationale: When two heterozygous parents (Tt × Tt) are crossed, the Punnett square
yields genotypes in the ratio 1 TT : 2 Tt : 1 tt. Since tall (T) is dominant over short (t),
both TT and Tt genotypes express the tall phenotype, while only tt expresses short. This
gives a 3:1 phenotypic ratio. Option A represents a test cross ratio, C describes
incomplete dominance, and D would result from a TT × TT or TT × Tt cross.
Q2: A woman with blood type A (heterozygous) marries a man with blood type B
(heterozygous). What is the probability their child will have blood type AB?
A. 0%
B. 25% [CORRECT]
C. 50%
D. 75%
Correct Answer: B
,Rationale: The mother is genotype Iᴬi and father is Iᴮi. The Punnett square yields: 25%
IᴬIᴮ (type AB), 25% Iᴬi (type A), 25% Iᴮi (type B), and 25% ii (type O). Only the IᴬIᴮ
genotype produces AB blood type. Option A ignores codominance, C confuses this with
one parent being homozygous, and D incorrectly assumes all combinations produce AB.
Q3: Which of the following best describes the Law of Independent Assortment?
A. Alleles for different traits separate during gamete formation
B. Allele pairs segregate independently of each other during gamete formation
[CORRECT]
C. Dominant alleles always mask recessive alleles
D. Genes on the same chromosome are always inherited together
Correct Answer: B
Rationale: Mendel's Law of Independent Assortment states that alleles of different
genes assort independently during gamete formation (applies to genes on different
chromosomes or far apart on the same chromosome). Option A describes the Law of
Segregation, C describes dominance relationships, and D describes genetic linkage,
which is an exception to independent assortment.
Q4: In a pedigree, an affected male has all affected daughters but no affected sons. The
unaffected mother has no affected children. What is the most likely mode of
inheritance?
A. Autosomal dominant
B. Autosomal recessive
C. X-linked dominant [CORRECT]
D. X-linked recessive
Correct Answer: C
, Rationale: X-linked dominant inheritance shows: (1) affected father passes X to ALL
daughters (who become affected) and Y to all sons (who remain unaffected), (2)
unaffected mother (XⁿXⁿ) cannot pass the trait. This matches the pedigree exactly.
Autosomal dominant would affect both sexes equally from affected fathers. X-linked
recessive would require carrier mothers for affected sons. Autosomal recessive would
skip generations.
Q5: A test cross is performed between an individual showing a dominant phenotype
(but unknown genotype) and a homozygous recessive individual. If the offspring show a
1:1 ratio of dominant to recessive phenotypes, what was the genotype of the unknown
parent?
A. Homozygous dominant
B. Heterozygous [CORRECT]
C. Homozygous recessive
D. Cannot be determined
Correct Answer: B
Rationale: A test cross reveals the unknown genotype through offspring ratios.
Unknown (A?) × aa. If 1:1 ratio results, the unknown parent produced both A and a
gametes equally, indicating genotype Aa (heterozygous). If AA, all offspring would show
dominant phenotype (Aa). If aa, the "dominant phenotype" parent couldn't be
homozygous recessive. The ratio definitively identifies heterozygosity.
Q6: In snapdragons, red flowers (CᴿCᴿ) crossed with white flowers (CᵂCᵂ) produce all
pink flowers (CᴿCᵂ). This is an example of:
A. Codominance
B. Incomplete dominance [CORRECT]
C. Multiple alleles
Questions & Answers Verified | Portage Learning | Pass
Guaranteed - A+ Graded
Q1: In a monohybrid cross between two heterozygous tall pea plants (Tt × Tt), what is
the expected phenotypic ratio in the offspring?
A. 1 tall : 1 short
B. 3 tall : 1 short [CORRECT]
C. 1 tall : 2 intermediate : 1 short
D. All tall
Correct Answer: B
Rationale: When two heterozygous parents (Tt × Tt) are crossed, the Punnett square
yields genotypes in the ratio 1 TT : 2 Tt : 1 tt. Since tall (T) is dominant over short (t),
both TT and Tt genotypes express the tall phenotype, while only tt expresses short. This
gives a 3:1 phenotypic ratio. Option A represents a test cross ratio, C describes
incomplete dominance, and D would result from a TT × TT or TT × Tt cross.
Q2: A woman with blood type A (heterozygous) marries a man with blood type B
(heterozygous). What is the probability their child will have blood type AB?
A. 0%
B. 25% [CORRECT]
C. 50%
D. 75%
Correct Answer: B
,Rationale: The mother is genotype Iᴬi and father is Iᴮi. The Punnett square yields: 25%
IᴬIᴮ (type AB), 25% Iᴬi (type A), 25% Iᴮi (type B), and 25% ii (type O). Only the IᴬIᴮ
genotype produces AB blood type. Option A ignores codominance, C confuses this with
one parent being homozygous, and D incorrectly assumes all combinations produce AB.
Q3: Which of the following best describes the Law of Independent Assortment?
A. Alleles for different traits separate during gamete formation
B. Allele pairs segregate independently of each other during gamete formation
[CORRECT]
C. Dominant alleles always mask recessive alleles
D. Genes on the same chromosome are always inherited together
Correct Answer: B
Rationale: Mendel's Law of Independent Assortment states that alleles of different
genes assort independently during gamete formation (applies to genes on different
chromosomes or far apart on the same chromosome). Option A describes the Law of
Segregation, C describes dominance relationships, and D describes genetic linkage,
which is an exception to independent assortment.
Q4: In a pedigree, an affected male has all affected daughters but no affected sons. The
unaffected mother has no affected children. What is the most likely mode of
inheritance?
A. Autosomal dominant
B. Autosomal recessive
C. X-linked dominant [CORRECT]
D. X-linked recessive
Correct Answer: C
, Rationale: X-linked dominant inheritance shows: (1) affected father passes X to ALL
daughters (who become affected) and Y to all sons (who remain unaffected), (2)
unaffected mother (XⁿXⁿ) cannot pass the trait. This matches the pedigree exactly.
Autosomal dominant would affect both sexes equally from affected fathers. X-linked
recessive would require carrier mothers for affected sons. Autosomal recessive would
skip generations.
Q5: A test cross is performed between an individual showing a dominant phenotype
(but unknown genotype) and a homozygous recessive individual. If the offspring show a
1:1 ratio of dominant to recessive phenotypes, what was the genotype of the unknown
parent?
A. Homozygous dominant
B. Heterozygous [CORRECT]
C. Homozygous recessive
D. Cannot be determined
Correct Answer: B
Rationale: A test cross reveals the unknown genotype through offspring ratios.
Unknown (A?) × aa. If 1:1 ratio results, the unknown parent produced both A and a
gametes equally, indicating genotype Aa (heterozygous). If AA, all offspring would show
dominant phenotype (Aa). If aa, the "dominant phenotype" parent couldn't be
homozygous recessive. The ratio definitively identifies heterozygosity.
Q6: In snapdragons, red flowers (CᴿCᴿ) crossed with white flowers (CᵂCᵂ) produce all
pink flowers (CᴿCᵂ). This is an example of:
A. Codominance
B. Incomplete dominance [CORRECT]
C. Multiple alleles
