Question 1

Which of the following best describes Mendel's Law of Segregation?

Accepted Answer

Two alleles for a gene separate during gamete formation, so each gamete receives only one allele.

Question 2

A true-breeding pea plant with purple flowers (PP) is crossed with a true-breeding plant with white flowers (pp). What is the expected genotype and phenotype ratio in the F1 generation?

Accepted Answer

Genotype: 100% Pp; Phenotype: 100% purple

Question 3

In a dihybrid cross between two heterozygous pea plants (YyRr x YyRr), what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 4

A man and a woman are both carriers for cystic fibrosis (heterozygous, Cc). What is the probability that their child will have cystic fibrosis?

Accepted Answer

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

Question 5

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both red blood cell shape and malaria resistance in humans.

Question 6

If a heterozygous individual (Pp) is crossed with a homozygous recessive individual (pp), what is the expected ratio of phenotypes in the offspring?

Accepted Answer

50% purple, 50% white

Question 7

Which inheritance pattern is illustrated by human blood types (A, B, AB, O)?

Accepted Answer

Codominance and multiple alleles

Question 8

A plant with genotype AaBb is self-crossed. Assuming independent assortment, what fraction of the offspring will have the genotype aabb?

Accepted Answer

$$\frac{1}{16}$$

Question 9

Which of the following best explains why traits can skip generations in a family pedigree?

Accepted Answer

Recessive alleles can be masked by dominant alleles in heterozygotes.

Question 10

In Labrador retrievers, coat color is determined by two genes: B (black) is dominant to b (brown), and E (pigment expression) is dominant to e (no pigment, yellow). What is the expected phenotype of a dog with genotype bbEe?

Accepted Answer

Brown

Question 11

Which of the following scenarios best illustrates polygenic inheritance?

Accepted Answer

Human skin color, which is influenced by several genes, resulting in a wide range of phenotypes.

Question 12

A woman with genotype IAi and a man with genotype IBi have a child. What is the probability that the child will have blood type O?

Accepted Answer

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

Question 13

Which of the following is an example of incomplete dominance?

Accepted Answer

A cross between red and white snapdragons produces pink offspring.

Question 14

A couple, both heterozygous for the sickle cell allele (Ss), have a child. What is the probability that the child will be a carrier (heterozygous) for sickle cell disease?

Accepted Answer

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

Question 15

Which of the following best describes the effect of environment on phenotype?

Accepted Answer

Environmental factors such as temperature and nutrition can influence the expression of genetic traits.

Question 16

A testcross is performed between a plant with an unknown genotype for a dominant trait and a homozygous recessive plant. If all offspring display the dominant phenotype, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant

Question 17

Which of the following best explains why consanguineous (related) matings increase the risk of recessive genetic disorders?

Accepted Answer

They increase the likelihood that both parents carry the same recessive allele.

Question 18

Which of the following is true about Huntington’s disease?

Accepted Answer

Symptoms usually appear after reproductive age.

Question 19

Which of the following best describes epistasis?

Accepted Answer

The expression of one gene is affected by another gene at a different locus.

Question 20

A couple undergoes genetic counseling and learns they are both carriers for Tay Sachs disease. What is the probability that their next two children will both be unaffected (not have the disease)?

Accepted Answer

$$\frac{9}{16}$$

Mendel and the Gene Idea: Patterns and Mechanisms of Inheritance

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