BIO 413 GENETICS AND GENOMICS
MIDTERM EXAM
Mendelian Genetics Molecular Inheritance Gene Mapping
Transcription and Regulation Questions and Answers Verified
Solutions 2026 2027
1. Which stage of meiosis is responsible for the physical segregation of homologous
chromosome pairs that underlies Mendel's First Law?
A. Prophase I
B. Anaphase I
C. Metaphase II
D. Anaphase II
Rationale: Homologous chromosomes separate during Anaphase I, ensuring that each resulting daughter
cell receives only one allele for each gene locus. Sister chromatids split later during Anaphase II.
2. What phenotypic ratio is expected from a monohybrid cross between two
heterozygous individuals displaying incomplete dominance?
A. 3:1
B. 1:2:1
C. 9:3:3:1
D. 2:1
Rationale: Under incomplete dominance, the heterozygous phenotype is intermediate between both
homozygous extremes. Crossing two heterozygotes yields a 1:2:1 phenotypic ratio that matches the
underlying genotypic ratio.
3. What term describes a cross used to determine whether an individual displaying a
dominant phenotype is homozygous dominant or heterozygous?
A. Testcross
B. Backcross
C. Reciprocal cross
D. Dihybrid cross
, Rationale: A testcross mates an individual of unknown dominant genotype with a homozygous recessive
individual. Observing recessive offspring confirms that the tested parent carried a recessive allele.
4. What non-Mendelian inheritance pattern allows both alleles to be fully expressed
simultaneously in a heterozygous individual, such as in AB blood types?
A. Incomplete dominance
B. Codominance
C. Overdominance
D. Epistasis
Rationale: Codominance occurs when both alleles contribute distinctly and equally to the phenotype. In
IAIB individuals, both A and B carbohydrate antigens are present on red blood cell surfaces.
5. What phenomenon produces a modified 9:7 dihybrid ratio when homozygous
recessive alleles at either of two loci mask the dominant alleles at both loci?
A. Duplicate recessive epistasis
B. Recessive epistasis
C. Dominant epistasis
D. Complementary gene action
Rationale: Duplicate recessive epistasis requires at least one functional dominant allele at both loci to
express the trait. Lacking a dominant allele at either locus yields the same recessive phenotype,
combining 3+3+1 into 7.
6. If two genes are completely linked on the same chromosome with no crossing over,
what is the maximum expected percentage of recombinant gametes?
A. 0%
B. 25%
C. 50%
D. 100%
Rationale: Complete linkage implies that no meiotic recombination occurs between the two loci.
Consequently, 100% of the produced gametes retain the parental allele combinations, yielding 0%
recombinants.
7. What is the maximum recombination frequency attainable between two genes located
very far apart on the same chromosome?
MIDTERM EXAM
Mendelian Genetics Molecular Inheritance Gene Mapping
Transcription and Regulation Questions and Answers Verified
Solutions 2026 2027
1. Which stage of meiosis is responsible for the physical segregation of homologous
chromosome pairs that underlies Mendel's First Law?
A. Prophase I
B. Anaphase I
C. Metaphase II
D. Anaphase II
Rationale: Homologous chromosomes separate during Anaphase I, ensuring that each resulting daughter
cell receives only one allele for each gene locus. Sister chromatids split later during Anaphase II.
2. What phenotypic ratio is expected from a monohybrid cross between two
heterozygous individuals displaying incomplete dominance?
A. 3:1
B. 1:2:1
C. 9:3:3:1
D. 2:1
Rationale: Under incomplete dominance, the heterozygous phenotype is intermediate between both
homozygous extremes. Crossing two heterozygotes yields a 1:2:1 phenotypic ratio that matches the
underlying genotypic ratio.
3. What term describes a cross used to determine whether an individual displaying a
dominant phenotype is homozygous dominant or heterozygous?
A. Testcross
B. Backcross
C. Reciprocal cross
D. Dihybrid cross
, Rationale: A testcross mates an individual of unknown dominant genotype with a homozygous recessive
individual. Observing recessive offspring confirms that the tested parent carried a recessive allele.
4. What non-Mendelian inheritance pattern allows both alleles to be fully expressed
simultaneously in a heterozygous individual, such as in AB blood types?
A. Incomplete dominance
B. Codominance
C. Overdominance
D. Epistasis
Rationale: Codominance occurs when both alleles contribute distinctly and equally to the phenotype. In
IAIB individuals, both A and B carbohydrate antigens are present on red blood cell surfaces.
5. What phenomenon produces a modified 9:7 dihybrid ratio when homozygous
recessive alleles at either of two loci mask the dominant alleles at both loci?
A. Duplicate recessive epistasis
B. Recessive epistasis
C. Dominant epistasis
D. Complementary gene action
Rationale: Duplicate recessive epistasis requires at least one functional dominant allele at both loci to
express the trait. Lacking a dominant allele at either locus yields the same recessive phenotype,
combining 3+3+1 into 7.
6. If two genes are completely linked on the same chromosome with no crossing over,
what is the maximum expected percentage of recombinant gametes?
A. 0%
B. 25%
C. 50%
D. 100%
Rationale: Complete linkage implies that no meiotic recombination occurs between the two loci.
Consequently, 100% of the produced gametes retain the parental allele combinations, yielding 0%
recombinants.
7. What is the maximum recombination frequency attainable between two genes located
very far apart on the same chromosome?
