Question 1

Gregor Mendel chose pea plants for his experiments primarily because:

Accepted Answer

They have a short generation time and produce many offspring.

Question 2

Which of the following best describes the Law of Segregation as stated by Mendel?

Accepted Answer

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

Question 3

A plant with genotype $$Tt ($$where $$T is $$tall and $$t is $$short) is crossed with a plant with genotype $$tt. $$What is the expected phenotypic ratio of the offspring?

Accepted Answer

1 tall : 1 short

Question 4

In a dihybrid cross between two heterozygous individuals ($$YyRr 	imes YyRr$$), where $$Y = $$yellow, $$y = $$green, $$R = $$round, $$r = $$wrinkled, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 5

Which of the following is an example of codominance?

Accepted Answer

A person with type AB blood expresses both A and B antigens equally.

Question 6

A testcross is performed to determine if a pea plant with a dominant phenotype is homozygous or heterozygous. Which cross would you perform?

Accepted Answer

Cross with a homozygous recessive plant.

Question 7

Which of the following best describes pleiotropy?

Accepted Answer

One gene affects multiple, seemingly unrelated phenotypic traits.

Question 8

A pedigree shows a trait that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 9

Which statement about the chromosomal theory of inheritance is correct?

Accepted Answer

Genes are located on chromosomes, which segregate and independently assort during meiosis.

Question 10

In Morgan’s fruit fly experiment, why did white-eyed males appear in the F2 generation but not in the F1 generation?

Accepted Answer

The white-eye allele is recessive and X-linked, so it is masked in F1 females but expressed in F2 males.

Question 11

Which of the following is true about X-inactivation in female mammals?

Accepted Answer

One X chromosome in each cell is randomly inactivated, forming a Barr body.

Question 12

A woman who is a carrier for an X-linked recessive disorder and a man who is unaffected have a son. What is the probability that their son will have the disorder?

Accepted Answer

$$0.5$$

Question 13

If two genes are linked and located close together on the same chromosome, which of the following is most likely?

Accepted Answer

They will be inherited together more often than not.

Question 14

A geneticist observes that two traits do not follow Mendel’s Law of Independent Assortment. Which explanation is most likely?

Accepted Answer

The genes are located on the same chromosome and are linked.

Question 15

Which of the following best describes aneuploidy?

Accepted Answer

A condition in which an organism has an abnormal number of chromosomes.

Question 16

A couple has a child with cystic fibrosis, an autosomal recessive disorder. Both parents are healthy. What are the genotypes of the parents?

Accepted Answer

Both are heterozygous carriers.

Question 17

Which of the following is an example of polygenic inheritance?

Accepted Answer

Human skin color, which is controlled by several genes.

Question 18

A man with blood type A (genotype $$I^A i) $$and a woman with blood type B (genotype $$I^B i) $$have a child. What is the probability that their child will have blood type O?

Accepted Answer

$$0.25$$

Question 19

Which of the following scenarios illustrates epistasis?

Accepted Answer

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

Question 20

If a child is born with Down syndrome due to nondisjunction, which of the following best explains the chromosomal abnormality?

Accepted Answer

The child has three copies of chromosome 21.

Mendelian Genetics and Chromosomal Basis of Inheritance: Study Guide

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