BIOD210 GENETICS | PORTAGE LEARNING | COMPLETE EXAM
PACKAGE 2026/2027 Exams 1-7 Complete Course Examination
Package | Actual Questions & Verified Answers | Comprehensive
Genetics Assessment | Pass Guarantee
BIOD210 Exam 1: Mendelian Foundations
Topics: Monohybrid/dihybrid crosses, probability, pedigrees, chromosomal inheritance
1. In garden peas, tall (T) is dominant to dwarf (t). If a heterozygous tall plant is crossed
with a dwarf plant, what is the expected phenotypic ratio of the offspring?
A. 3 tall : 1 dwarf
B. 1 tall : 1 dwarf
C. All tall
D. All dwarf
Correct Answer: B
Rationale: This is a test cross (Tt × tt). The heterozygote produces gametes T and t
(50% each). The dwarf parent produces only t. The Punnett square yields 50% Tt (tall)
and 50% tt (dwarf), giving a 1:1 phenotypic ratio. Option A represents a monohybrid
cross between two heterozygotes (Tt × Tt). Options C and D represent homozygous
crosses.
2. A true-breeding purple-flowered pea plant is crossed with a true-breeding
white-flowered plant. The F1 generation is allowed to self-fertilize. What is the expected
phenotypic ratio in the F2 generation?
A. 1 purple : 1 white
B. 3 purple : 1 white
,C. 9 purple : 3 white
D. All purple
Correct Answer: B
Rationale: This describes Mendel's classic monohybrid cross. True-breeding parents are
PP (purple) and pp (white). F1 is all Pp (purple). F2 from Pp × Pp yields genotypic ratio 1
PP : 2 Pp : 1 pp, which phenotypically is 3 purple (PP + Pp) : 1 white (pp). Option A is a
test cross ratio. Option C is a dihybrid ratio.
3. In humans, the allele for free earlobes (E) is dominant over attached earlobes (e). If
two parents with free earlobes have a child with attached earlobes, what must be the
genotypes of the parents?
A. EE × EE
B. EE × Ee
C. Ee × Ee
D. Ee × ee
Correct Answer: C
Rationale: For two parents with the dominant phenotype to produce a recessive
offspring (ee), both must carry the recessive allele. Therefore, both parents must be
heterozygous (Ee). The cross Ee × Ee yields 25% ee offspring. Option A produces all EE.
Option B produces all dominant phenotypes (50% EE, 50% Ee). Option D is a test cross.
4. What is the probability of rolling a 6 on a fair six-sided die and flipping heads on a fair
coin in the same trial?
A. 1/12
B. 1/6
,C. 1/4
D. 1/2
Correct Answer: A
Rationale: These are independent events. Probability of rolling 6 = 1/6. Probability of
heads = 1/2. By the product rule: 1/6 × 1/2 = 1/12. Option B is just the die probability.
Option C is the probability of two coin flips both being heads.
5. In a dihybrid cross between two heterozygous pea plants (RrYy × RrYy), where R =
round (dominant) and Y = yellow (dominant), what proportion of offspring will be
homozygous recessive for both traits?
A. 1/16
B. 1/8
C. 1/4
D. 9/16
Correct Answer: A
Rationale: For each gene, the probability of homozygous recessive (rr or yy) is 1/4. For
both simultaneously: 1/4 × 1/4 = 1/16. This represents the rryy genotype in the 9:3:3:1
phenotypic ratio (the 1 in the double recessive category).
6. Which of the following best describes the Law of Independent Assortment?
A. Alleles segregate into gametes in pairs
B. Genes for different traits separate independently during gamete formation
C. Dominant alleles always mask recessive alleles
D. Gametes receive only one allele for each gene
, Correct Answer: B
Rationale: Mendel's Law of Independent Assortment states that alleles of different
genes assort independently of one another during gamete formation (applies to genes
on different chromosomes or far apart on the same chromosome). Option A describes
the Law of Segregation. Option C describes dominance. Option D describes haploid
gametes.
7. A couple has three children, all girls. What is the probability that their fourth child will
be a boy?
A. 1/8
B. 1/4
C. 1/2
D. 3/4
Correct Answer: C
Rationale: Each conception is an independent event with a 50% probability of male or
female (assuming equal viability). Previous outcomes do not influence future
probabilities (gambler's fallacy). The probability remains 1/2 for each birth.
8. In a pedigree analysis, a trait appears in every generation and affects both males and
females equally. Both parents pass the trait to offspring. What is the most likely mode
of inheritance?
A. Autosomal recessive
B. Autosomal dominant
C. X-linked recessive
D. Y-linked
PACKAGE 2026/2027 Exams 1-7 Complete Course Examination
Package | Actual Questions & Verified Answers | Comprehensive
Genetics Assessment | Pass Guarantee
BIOD210 Exam 1: Mendelian Foundations
Topics: Monohybrid/dihybrid crosses, probability, pedigrees, chromosomal inheritance
1. In garden peas, tall (T) is dominant to dwarf (t). If a heterozygous tall plant is crossed
with a dwarf plant, what is the expected phenotypic ratio of the offspring?
A. 3 tall : 1 dwarf
B. 1 tall : 1 dwarf
C. All tall
D. All dwarf
Correct Answer: B
Rationale: This is a test cross (Tt × tt). The heterozygote produces gametes T and t
(50% each). The dwarf parent produces only t. The Punnett square yields 50% Tt (tall)
and 50% tt (dwarf), giving a 1:1 phenotypic ratio. Option A represents a monohybrid
cross between two heterozygotes (Tt × Tt). Options C and D represent homozygous
crosses.
2. A true-breeding purple-flowered pea plant is crossed with a true-breeding
white-flowered plant. The F1 generation is allowed to self-fertilize. What is the expected
phenotypic ratio in the F2 generation?
A. 1 purple : 1 white
B. 3 purple : 1 white
,C. 9 purple : 3 white
D. All purple
Correct Answer: B
Rationale: This describes Mendel's classic monohybrid cross. True-breeding parents are
PP (purple) and pp (white). F1 is all Pp (purple). F2 from Pp × Pp yields genotypic ratio 1
PP : 2 Pp : 1 pp, which phenotypically is 3 purple (PP + Pp) : 1 white (pp). Option A is a
test cross ratio. Option C is a dihybrid ratio.
3. In humans, the allele for free earlobes (E) is dominant over attached earlobes (e). If
two parents with free earlobes have a child with attached earlobes, what must be the
genotypes of the parents?
A. EE × EE
B. EE × Ee
C. Ee × Ee
D. Ee × ee
Correct Answer: C
Rationale: For two parents with the dominant phenotype to produce a recessive
offspring (ee), both must carry the recessive allele. Therefore, both parents must be
heterozygous (Ee). The cross Ee × Ee yields 25% ee offspring. Option A produces all EE.
Option B produces all dominant phenotypes (50% EE, 50% Ee). Option D is a test cross.
4. What is the probability of rolling a 6 on a fair six-sided die and flipping heads on a fair
coin in the same trial?
A. 1/12
B. 1/6
,C. 1/4
D. 1/2
Correct Answer: A
Rationale: These are independent events. Probability of rolling 6 = 1/6. Probability of
heads = 1/2. By the product rule: 1/6 × 1/2 = 1/12. Option B is just the die probability.
Option C is the probability of two coin flips both being heads.
5. In a dihybrid cross between two heterozygous pea plants (RrYy × RrYy), where R =
round (dominant) and Y = yellow (dominant), what proportion of offspring will be
homozygous recessive for both traits?
A. 1/16
B. 1/8
C. 1/4
D. 9/16
Correct Answer: A
Rationale: For each gene, the probability of homozygous recessive (rr or yy) is 1/4. For
both simultaneously: 1/4 × 1/4 = 1/16. This represents the rryy genotype in the 9:3:3:1
phenotypic ratio (the 1 in the double recessive category).
6. Which of the following best describes the Law of Independent Assortment?
A. Alleles segregate into gametes in pairs
B. Genes for different traits separate independently during gamete formation
C. Dominant alleles always mask recessive alleles
D. Gametes receive only one allele for each gene
, Correct Answer: B
Rationale: Mendel's Law of Independent Assortment states that alleles of different
genes assort independently of one another during gamete formation (applies to genes
on different chromosomes or far apart on the same chromosome). Option A describes
the Law of Segregation. Option C describes dominance. Option D describes haploid
gametes.
7. A couple has three children, all girls. What is the probability that their fourth child will
be a boy?
A. 1/8
B. 1/4
C. 1/2
D. 3/4
Correct Answer: C
Rationale: Each conception is an independent event with a 50% probability of male or
female (assuming equal viability). Previous outcomes do not influence future
probabilities (gambler's fallacy). The probability remains 1/2 for each birth.
8. In a pedigree analysis, a trait appears in every generation and affects both males and
females equally. Both parents pass the trait to offspring. What is the most likely mode
of inheritance?
A. Autosomal recessive
B. Autosomal dominant
C. X-linked recessive
D. Y-linked
