BIOD 101 / BIOD101 Essential Biology I W/Lab Module
4 Exam Actual 2025/2026 with Detailed Rationales |
100% Verified | Pass Guaranteed – A+ Graded
SECTION 1: GENETICS & HEREDITY (12 Questions)
Q1: In garden peas, tall stem height (T) is dominant to dwarf (t). If a heterozygous tall
plant is crossed with a homozygous dwarf plant, what is the expected phenotypic
ratio of the offspring?
A. 3 tall : 1 dwarf
B. 1 tall : 1 dwarf [CORRECT]
C. All tall
D. All dwarf
Correct Answer: B
Rationale: Correct because a Tt × tt cross produces 50% Tt (tall) and 50% tt (dwarf)
offspring, yielding a 1:1 phenotypic ratio in the progeny.
Q2: In humans, a widow's peak hairline (W) is dominant over a straight hairline (w). If
two heterozygous parents (Ww) have a child, what is the probability that the child will
have a straight hairline?
A. 0%
B. 25% [CORRECT]
,C. 50%
D. 75%
Correct Answer: B
Rationale: Correct because a Ww × Ww cross yields genotypes in a 1:2:1 ratio, with
only the homozygous recessive ww offspring (25%) expressing the straight hairline
phenotype.
Q3: In snapdragons, a cross between a true-breeding red-flowered plant (RR) and a
true-breeding white-flowered plant (rr) produces offspring that are all pink (Rr). This
inheritance pattern is an example of:
A. Complete dominance
B. Codominance
C. Incomplete dominance [CORRECT]
D. Multiple alleles
Correct Answer: C
Rationale: Correct because incomplete dominance produces an intermediate
phenotype in heterozygotes; the pink flowers blend the parental red and white
phenotypes rather than showing either fully.
Q4: A person with type AB blood has children with a person with type O blood. What
blood types are possible among their children?
A. A and B only [CORRECT]
B. A, B, AB, and O
, C. AB and O only
D. Type A only
Correct Answer: A
Rationale: Correct because the AB parent can contribute either an A or B allele, while
the O parent can only contribute an O allele, resulting in children with either type A
(AO) or type B (BO) blood.
Q5: Red-green color blindness is an X-linked recessive trait. If a color-blind man (XⁿY)
has a child with a woman who is a carrier (XᴺXⁿ), what is the probability that their
son will be color-blind?
A. 0%
B. 25%
C. 50% [CORRECT]
D. 100%
Correct Answer: C
Rationale: Correct because the carrier mother has a 50% chance of passing the Xⁿ
allele to any son, who will express color blindness since he receives a Y
chromosome from his father.
Q6: Which inheritance pattern is characterized by affected individuals in every
generation, no skipped generations, and affected fathers passing the trait to all
daughters but no sons?
A. Autosomal recessive
B. Autosomal dominant
4 Exam Actual 2025/2026 with Detailed Rationales |
100% Verified | Pass Guaranteed – A+ Graded
SECTION 1: GENETICS & HEREDITY (12 Questions)
Q1: In garden peas, tall stem height (T) is dominant to dwarf (t). If a heterozygous tall
plant is crossed with a homozygous dwarf plant, what is the expected phenotypic
ratio of the offspring?
A. 3 tall : 1 dwarf
B. 1 tall : 1 dwarf [CORRECT]
C. All tall
D. All dwarf
Correct Answer: B
Rationale: Correct because a Tt × tt cross produces 50% Tt (tall) and 50% tt (dwarf)
offspring, yielding a 1:1 phenotypic ratio in the progeny.
Q2: In humans, a widow's peak hairline (W) is dominant over a straight hairline (w). If
two heterozygous parents (Ww) have a child, what is the probability that the child will
have a straight hairline?
A. 0%
B. 25% [CORRECT]
,C. 50%
D. 75%
Correct Answer: B
Rationale: Correct because a Ww × Ww cross yields genotypes in a 1:2:1 ratio, with
only the homozygous recessive ww offspring (25%) expressing the straight hairline
phenotype.
Q3: In snapdragons, a cross between a true-breeding red-flowered plant (RR) and a
true-breeding white-flowered plant (rr) produces offspring that are all pink (Rr). This
inheritance pattern is an example of:
A. Complete dominance
B. Codominance
C. Incomplete dominance [CORRECT]
D. Multiple alleles
Correct Answer: C
Rationale: Correct because incomplete dominance produces an intermediate
phenotype in heterozygotes; the pink flowers blend the parental red and white
phenotypes rather than showing either fully.
Q4: A person with type AB blood has children with a person with type O blood. What
blood types are possible among their children?
A. A and B only [CORRECT]
B. A, B, AB, and O
, C. AB and O only
D. Type A only
Correct Answer: A
Rationale: Correct because the AB parent can contribute either an A or B allele, while
the O parent can only contribute an O allele, resulting in children with either type A
(AO) or type B (BO) blood.
Q5: Red-green color blindness is an X-linked recessive trait. If a color-blind man (XⁿY)
has a child with a woman who is a carrier (XᴺXⁿ), what is the probability that their
son will be color-blind?
A. 0%
B. 25%
C. 50% [CORRECT]
D. 100%
Correct Answer: C
Rationale: Correct because the carrier mother has a 50% chance of passing the Xⁿ
allele to any son, who will express color blindness since he receives a Y
chromosome from his father.
Q6: Which inheritance pattern is characterized by affected individuals in every
generation, no skipped generations, and affected fathers passing the trait to all
daughters but no sons?
A. Autosomal recessive
B. Autosomal dominant
