Question 1

In the context of Mendelian genetics, what is the expected phenotypic ratio for the offspring of a heterozygous cross ($$Bb 	imes Bb) $$for a dominant purple flower trait, as shown in the first image?

Accepted Answer

3 purple : 1 white

Question 2

A pedigree shows that a trait appears in every generation and affects both males and females equally. Which mode of inheritance is most likely responsible for this pattern?

Accepted Answer

Autosomal dominant

Question 3

If two parents are both carriers for albinism ($$Aa 	imes Aa$$), what is the probability that their child will have albinism? Use the Punnett square shown in the study materials.

Accepted Answer

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

Question 4

A woman with genotype $$X^HX^h ($$carrier for hemophilia) and a man with genotype $$X^hY ($$hemophiliac) have children. What proportion of their offspring will have hemophilia?

Accepted Answer

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

Question 5

Which of the following best explains why X-linked recessive disorders are more common in males than in females?

Accepted Answer

Males are hemizygous for the X chromosome, so a single recessive allele will cause the disorder.

Question 6

A couple has a child with Tay-Sachs disease, but neither parent nor anyone in their families has the disease. What is the most accurate statement a genetic counselor should make?

Accepted Answer

Because you have had one child with Tay-Sachs, you must each carry the allele. Any child you have has a 25% chance of having the disease.

Question 7

Which law states that alleles of genes on nonhomologous chromosomes assort independently during gamete formation?

Accepted Answer

Law of Independent Assortment

Question 8

A tortoiseshell cat is a phenotypic example of which genetic phenomenon?

Accepted Answer

X-inactivation in female mammals

Question 9

In sickle-cell disease, heterozygotes ($$Hb^A Hb^S) $$are usually healthy but may suffer some symptoms. What is the term for this phenomenon?

Accepted Answer

Incomplete dominance

Question 10

If a gene is located on the Y chromosome, what is the expected pattern of inheritance?

Accepted Answer

Only males will inherit the trait from their fathers.

Question 11

A pedigree shows that a trait skips generations and appears only in males. Which mode of inheritance is most likely responsible?

Accepted Answer

X-linked recessive

Question 12

What is the probability that two heterozygous parents ($$Dd 	imes Dd) $$for achondroplasia (a dominant disorder) will have a child with normal bone growth?

Accepted Answer

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

Question 13

Which of the following best describes the behavior of chromosomes during meiosis that supports Mendel’s law of segregation?

Accepted Answer

Homologous chromosomes separate, and alleles segregate into different gametes.

Question 14

A woman with genotype $$X^NX^n ($$carrier for an X-linked recessive disorder) marries a man with genotype $$X^NY ($$normal). What proportion of their sons will have the disorder?

Accepted Answer

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

Question 15

Which of the following is a real-world example of a recessively inherited disorder caused by a malfunctioning protein?

Accepted Answer

Albinism

Question 16

In a dihybrid cross ($$YyRr 	imes YyRr$$), what is the expected phenotypic ratio in the F2 generation according to Mendel’s laws?

Accepted Answer

9:3:3:1

Question 17

Which of the following statements about carriers of recessive genetic disorders is correct?

Accepted Answer

Carriers are heterozygous and phenotypically normal.

Question 18

Which rule is used to predict the probability of two independent events both occurring, such as inheriting two recessive alleles for different traits?

Accepted Answer

Multiplication rule

Question 19

A calico cat displays patches of black and orange fur. What genetic mechanism is responsible for this mosaic phenotype?

Accepted Answer

Random X chromosome inactivation

Question 20

Which of the following best describes the chromosome theory of inheritance?

Accepted Answer

Genes are located on chromosomes, and chromosomes undergo segregation and independent assortment during meiosis.

Mendelian Genetics and Chromosomal Basis of Inheritance

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