Question 1

Which of the following best describes incomplete dominance in a genetic cross?

Accepted Answer

The heterozygote expresses an intermediate phenotype between the two parents.

Question 2

In snapdragons, red flowers ($A^1A^1$) are crossed with white flowers ($A^2A^2$). What is the expected phenotypic ratio in the $F_2$ generation?

Accepted Answer

$1$ red : $2$ pink : $1$ white

Question 3

Which statement about codominance is correct?

Accepted Answer

Codominance results in the heterozygote expressing traits from both parents simultaneously.

Question 4

A person with genotype $I^A I^B$ for the ABO blood group will have which blood type?

Accepted Answer

Type AB

Question 5

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both respiratory function and fertility.

Question 6

In mice, the $A^Y$ allele of the agouti gene is dominant for coat color but recessive for lethality. What is the expected ratio of yellow to agouti offspring when two yellow mice ($A^Y A$) are crossed?

Accepted Answer

$2$ yellow : $1$ agouti

Question 7

Which of the following best explains why the $A^Y A^Y$ genotype is not observed in mice?

Accepted Answer

The $A^Y$ allele is recessive for lethality, so homozygotes do not survive.

Question 8

Which of the following is true regarding the dominance relationships in the ABO blood group system?

Accepted Answer

$I^A$ and $I^B$ are codominant to each other and both are dominant to $i$.

Question 9

A population of lentils has five alleles for seed coat pattern: marbled-1, marbled-2, spotted, dotted, and clear. If marbled-1 is dominant over all other alleles, what would be the phenotype of a plant with genotype marbled-1/clear?

Accepted Answer

Marbled-1

Question 10

Which of the following statements about allele frequency is correct?

Accepted Answer

Allele frequency is the percentage of the total number of gene copies for one allele in a population.

Question 11

Which of the following is a consequence of pleiotropy in sickle-cell anemia?

Accepted Answer

The sickle-cell allele affects multiple traits, including anemia, heart failure, and resistance to malaria.

Question 12

Which of the following best describes a monomorphic gene?

Accepted Answer

A gene with only one common wild-type allele.

Question 13

A mutation in a gene required for both cilia and flagella function in humans leads to which phenomenon?

Accepted Answer

Pleiotropy

Question 14

If a gene has 400 to 1200 alleles and each genotype produces a distinct phenotype, which genetic system does this describe?

Accepted Answer

Human histocompatibility antigens (HLA genes)

Question 15

Which of the following statements about mutations is correct?

Accepted Answer

Mutations are chance alterations of genetic material that arise spontaneously.

Question 16

In the context of Mendelian genetics, which statement is true regarding dominance relations?

Accepted Answer

Dominance relations do not affect the transmission of alleles; Mendel's laws of segregation still apply.

Question 17

Which genotype would result in a mouse with black fur only, given the agouti gene alleles $A$ and $a$?

Accepted Answer

$aa$

Question 18

Which of the following is NOT a reason why some traits do not follow simple Mendelian inheritance?

Accepted Answer

All traits are determined by a single allele

Question 19

Which of the following is true about the phenotype of a heterozygote in complete dominance?

Accepted Answer

It resembles one of the two parents.

Extensions of Mendelian Inheritance: Single-Gene and Multi-Gene Interactions

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