Question 1

Which of the following statements best explains why Marfan syndrome is considered a dominant genetic disorder?

Accepted Answer

A single defective copy of the Marfan gene is enough to cause the syndrome.

Question 2

In Mendel's experiments with pea plants, what was the observed phenotypic ratio in the F2 generation when crossing true-breeding purple-flowered and white-flowered plants?

Accepted Answer

3:1 (purple:white)

Question 3

Which of the following best describes Mendel's law of segregation?

Accepted Answer

Homologous chromosomes separate randomly during meiosis, so each gamete receives only one allele of each gene.

Question 4

A plant with genotype Pp (where P is dominant for purple flowers and p is recessive for white flowers) self-fertilizes. What fraction of its offspring will have white flowers?

Accepted Answer

$$\frac{1}{4}$$

Question 5

Which of the following is an example of incomplete dominance?

Accepted Answer

Palomino horses, where heterozygotes have a golden coat intermediate between chestnut and cremello.

Question 6

If a person with genotype Ao for blood type mates with a person with genotype Bo, what are the possible blood types of their children?

Accepted Answer

Type A, type B, type AB, and type O

Question 7

Which genetic phenomenon is illustrated when a single gene mutation causes multiple symptoms, such as the 'nude' mouse with immune and skin defects?

Accepted Answer

Pleiotropy

Question 8

A test cross is performed between a pea plant with a dominant phenotype of unknown genotype and a homozygous recessive plant. If half the offspring show the recessive phenotype, what is the genotype of the unknown parent?

Accepted Answer

Heterozygous

Question 9

In a dihybrid cross between SsYy x SsYy pea plants (S = smooth, s = wrinkled, Y = yellow, y = green), what is the expected phenotypic ratio among the offspring?

Accepted Answer

9:3:3:1

Question 10

Which process during meiosis is responsible for the independent assortment of genes located on different chromosomes?

Accepted Answer

Random orientation of homologous pairs during metaphase I

Question 11

A woman who is heterozygous for the X-linked recessive allele for red-green color blindness (XNXn) has children with a man who has normal color vision (XNY). What is the probability that their sons will be color blind?

Accepted Answer

$$\frac{1}{2}$$

Question 12

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes contribute to a single trait, resulting in a range of phenotypes.

Question 13

Which statement about sex-linked traits is correct?

Accepted Answer

Females must inherit two copies of a recessive X-linked allele to express the trait.

Question 14

Which of the following is true regarding linked genes?

Accepted Answer

They tend to be inherited together because they are located on the same chromosome.

Question 15

A person with sickle-cell anemia has which genotype for the hemoglobin gene?

Accepted Answer

Homozygous recessive (two defective alleles)

Question 16

Which equation represents the expected genotype ratio for a monohybrid cross between two heterozygous individuals (Aa x Aa)?

Accepted Answer

$$1\,AA : 2\,Aa : 1\,aa$$

Question 17

Which of the following best explains why the phenotype of Siamese cats is affected by temperature?

Accepted Answer

The enzyme responsible for dark pigment is inactive above $$34^\circ\mathrm{C}.$$

Question 18

Which of the following is an example of codominance?

Accepted Answer

A person with AB blood type expressing both A and B glycoproteins.

Question 19

If a genetic disorder is autosomal dominant, what is the probability that a child will inherit the disorder if one parent is heterozygous and the other is homozygous recessive?

Accepted Answer

$$\frac{1}{2}$$

Patterns of Inheritance: Mendelian Genetics and Beyond

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