Question 1

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

Accepted Answer

Alleles for a heritable character separate during gamete formation, so that each gamete carries only one allele for each gene.

Question 2

A plant with genotype $$Tt ($$where $$T is $$dominant for tall and $$t is $$recessive for short) is crossed with another $$Tt$$ plant. What is the expected phenotypic ratio of tall to short plants in the F2 generation?

Accepted Answer

$$3:1$$

Question 3

Which of the following scenarios is an example of incomplete dominance?

Accepted Answer

A pink-flowered snapdragon results from crossing a red-flowered plant with a white-flowered plant.

Question 4

In a dihybrid cross between two individuals heterozygous for both traits ($$YyRr 	imes YyRr$$), what is the expected phenotypic ratio in the F2 generation, assuming independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 5

Which of the following best explains why Huntington’s disease, a late-acting lethal dominant disorder, persists in human populations?

Accepted Answer

Symptoms appear after reproductive age, allowing carriers to pass on the allele before dying.

Question 6

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene causes multiple symptoms in cystic fibrosis, such as lung infections and digestive problems.

Question 7

A man with blood type $$IAIB$$ and a woman with blood type $$ii$$ have children. Which blood types are possible for their offspring?

Accepted Answer

Type A and Type B only

Question 8

Which of the following best describes the difference between genotype and phenotype?

Accepted Answer

Genotype refers to the genetic makeup, while phenotype refers to the observable traits.

Question 9

In a family, both parents are carriers for cystic fibrosis (genotype $$Cc). $$What is the probability that their child will have cystic fibrosis?

Accepted Answer

$$1/4$$

Question 10

Which of the following best illustrates polygenic inheritance?

Accepted Answer

Height in humans, which shows continuous variation

Question 11

If a true-breeding purple-flowered pea plant ($$PP) is $$crossed with a true-breeding white-flowered pea plant ($$pp$$), what will be the genotype and phenotype of the F1 generation?

Accepted Answer

All $$Pp ($$purple)

Question 12

Which of the following statements about Mendel’s law of independent assortment is correct?

Accepted Answer

It explains why alleles for different traits are inherited independently if they are on different chromosomes.

Question 13

Which of the following is an example of epistasis?

Accepted Answer

A gene for pigment deposition masks the expression of a gene for pigment color in Labrador retrievers.

Question 14

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

Accepted Answer

$$1/4$$

Question 15

Which of the following best describes codominance?

Accepted Answer

Both alleles in the heterozygote are fully expressed.

Question 16

A genetic counselor is working with a couple, both of whom are heterozygous for the Tay-Sachs allele ($$Tt). $$What is the probability that their first child will be a carrier but not affected by the disease?

Accepted Answer

$$1/2$$

Question 17

Which of the following best explains why sickle-cell anemia is more common in certain populations?

Accepted Answer

The sickle-cell allele provides resistance to malaria in heterozygotes.

Question 18

Which of the following is true about the F2 generation in a monohybrid cross between two heterozygotes ($$Aa 	imes Aa$$)?

Accepted Answer

The genotypic ratio is $$1:2:1$$ and the phenotypic ratio is $$3:1.$$

Question 19

Which of the following best describes a true-breeding organism?

Accepted Answer

It produces offspring with the same phenotype when self-fertilized.

Question 20

A Punnett square is used to predict the outcome of a genetic cross. In a cross between $$Aa$$ and $$aa$$, what is the probability that an offspring will be homozygous recessive?

Accepted Answer

$$1/2$$

Mendel and the Gene Idea: Patterns and Complexities of Inheritance

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