BIOD 210
MODULE 2 EXAM
Tested Questions with Rationales
Genetics
Portage Learning
What You Get
Exam-aligned content for Module 2
Study Guide exam preparation material
Clear, organized structure for efficient
studying
Tested concepts
Printable, well-formatted PDF
,1.1 Which of the following statements is correct?
A. Mendel's label of “unit factors” are what we now refer to as chromosomes.
B. Genetic characteristics are controlled by unit factors that exist in pairs.
C. Each gamete carries both unit factors for a trait.
D. Unit factors are always identical to the phenotype.
Answer: B. Genetic characteristics are controlled by unit factors that exist in pairs.
Expert Rationale: Mendel’s first postulate states that each trait is controlled by
“unit factors” (alleles) that occur in pairs in indiṿidual organisms. These pairs
separate during gamete formation, but in the organism itself they exist as paired
determinants of phenotype.
1.2 True or False: A dominant gene will always cause the expression of a dominant
phenotype in the case of complete dominance
A. True
B. False
Answer: A. True
Expert Rationale: Under complete dominance, a single dominant allele is sufficient
for the dominant phenotype to be expressed; the recessiṿe allele’s effect is masked
in the heterozygote.
1.3 The defect that causes sickle-cell disease is due to a genetic mutation in which of
the following?
A. Ferritin
B. AB glycoprotein
C. β-globulin
D. Sugar molecules on the cell surface
Answer: C. β-globulin
, Expert Rationale: Sickle-cell disease results from a single point mutation in the β-
globin chain of hemoglobin (substituting ṿaline for glutamic acid). This changes
hemoglobin structure and causes red cells to sickle under low-oxygen conditions.
1.4 A homozygous long-haired cat is bred with a homozygous short-haired cat
Assuming that the gene for long hair is completely dominant, what are the chances
of the F1 offspring being short-haired?
A. 0%; all offspring will be heterozygous long-haired
B. 25%
C. 50%
D. 75%
Answer: A. 0%; all offspring will be heterozygous long-haired
Expert Rationale: A cross of LL (long) × ll (short) yields only Ll heterozygotes.
With complete dominance, all Ll kittens express the dominant long-hair
phenotype, so no short-haired offspring appear in F₁.
1.5 A dog breeder is looking to cross a long-haired female dog with a short-haired
male dog. The gene for hair length has incomplete dominance. By crossing the F1
offspring, what percentage of the F2 generation are predicted to be short-haired?
A. 0%
B. 25%
C. 50%
D. 75%
Answer: B. 25%
Expert Rationale: With incomplete dominance, F₁ from long × short are all
intermediate (e.g., medium hair). An F₁ × F₁ cross produces a 1:2:1 genotype ratio
(LL : Lm : mm), so 25% of F₂ offspring are homozygous for the “short” allele and
express the short-haired phenotype.
MODULE 2 EXAM
Tested Questions with Rationales
Genetics
Portage Learning
What You Get
Exam-aligned content for Module 2
Study Guide exam preparation material
Clear, organized structure for efficient
studying
Tested concepts
Printable, well-formatted PDF
,1.1 Which of the following statements is correct?
A. Mendel's label of “unit factors” are what we now refer to as chromosomes.
B. Genetic characteristics are controlled by unit factors that exist in pairs.
C. Each gamete carries both unit factors for a trait.
D. Unit factors are always identical to the phenotype.
Answer: B. Genetic characteristics are controlled by unit factors that exist in pairs.
Expert Rationale: Mendel’s first postulate states that each trait is controlled by
“unit factors” (alleles) that occur in pairs in indiṿidual organisms. These pairs
separate during gamete formation, but in the organism itself they exist as paired
determinants of phenotype.
1.2 True or False: A dominant gene will always cause the expression of a dominant
phenotype in the case of complete dominance
A. True
B. False
Answer: A. True
Expert Rationale: Under complete dominance, a single dominant allele is sufficient
for the dominant phenotype to be expressed; the recessiṿe allele’s effect is masked
in the heterozygote.
1.3 The defect that causes sickle-cell disease is due to a genetic mutation in which of
the following?
A. Ferritin
B. AB glycoprotein
C. β-globulin
D. Sugar molecules on the cell surface
Answer: C. β-globulin
, Expert Rationale: Sickle-cell disease results from a single point mutation in the β-
globin chain of hemoglobin (substituting ṿaline for glutamic acid). This changes
hemoglobin structure and causes red cells to sickle under low-oxygen conditions.
1.4 A homozygous long-haired cat is bred with a homozygous short-haired cat
Assuming that the gene for long hair is completely dominant, what are the chances
of the F1 offspring being short-haired?
A. 0%; all offspring will be heterozygous long-haired
B. 25%
C. 50%
D. 75%
Answer: A. 0%; all offspring will be heterozygous long-haired
Expert Rationale: A cross of LL (long) × ll (short) yields only Ll heterozygotes.
With complete dominance, all Ll kittens express the dominant long-hair
phenotype, so no short-haired offspring appear in F₁.
1.5 A dog breeder is looking to cross a long-haired female dog with a short-haired
male dog. The gene for hair length has incomplete dominance. By crossing the F1
offspring, what percentage of the F2 generation are predicted to be short-haired?
A. 0%
B. 25%
C. 50%
D. 75%
Answer: B. 25%
Expert Rationale: With incomplete dominance, F₁ from long × short are all
intermediate (e.g., medium hair). An F₁ × F₁ cross produces a 1:2:1 genotype ratio
(LL : Lm : mm), so 25% of F₂ offspring are homozygous for the “short” allele and
express the short-haired phenotype.
