Question 1

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

Accepted Answer

Pairs of alleles are separated during meiosis I in the formation of gametes.

Question 2

A pea plant with genotype $$Rr ($$where $$R is $$dominant for round seeds and $$r is $$recessive for wrinkled seeds) is self-fertilized. What is the expected phenotypic ratio of the offspring?

Accepted Answer

$$3:1 ($$round:wrinkled)

Question 3

Which of the following is an example of codominance in humans?

Accepted Answer

ABO blood group, where individuals with genotype $$I^A I^B$$ express both A and B antigens.

Question 4

In a dihybrid cross between two heterozygous pea plants ($$RrYy 	imes RrYy$$), what is the expected phenotypic ratio in the $$F_2$$ generation if the genes assort independently?

Accepted Answer

$$9:3:3:1$$

Question 5

A woman who is a carrier for an X-linked recessive trait (e.g., red-green color blindness) has children with a man who does not have the trait. What is the probability that their son will be affected?

Accepted Answer

$$0.5$$

Question 6

Which of the following best explains why linked genes do not always stay together during inheritance?

Accepted Answer

Crossing over during prophase I of meiosis can separate linked genes.

Question 7

A testcross is performed between a pea plant with an unknown genotype for seed shape (dominant phenotype) and a homozygous recessive plant. If all offspring have round seeds, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant ($$RR)$$

Question 8

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causing multiple symptoms in Marfan syndrome.

Question 9

If a trait appears equally in males and females and can skip generations, what is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 10

Which of the following statements about quantitative traits is correct?

Accepted Answer

They are influenced by multiple genes and often show a bell-shaped distribution.

Question 11

A child is born with phenylketonuria (PKU), a genetic disorder. If the child is placed on a low-phenylalanine diet, they develop normally. What does this illustrate?

Accepted Answer

The environment can influence the phenotype expressed by a genotype.

Question 12

Which of the following best describes epistasis?

Accepted Answer

The expression of one gene is masked by the genotype of another gene.

Question 13

In a pedigree, a trait is observed in every generation and affected individuals have at least one affected parent. What is the most likely inheritance pattern?

Accepted Answer

Autosomal dominant

Question 14

Which of the following is true about the chromosome theory of inheritance?

Accepted Answer

Genes are located on chromosomes, and their physical separation during meiosis explains Mendel’s principles.

Question 15

A man with an X-linked dominant disorder has children with a woman who does not have the disorder. Which of the following is true about their children?

Accepted Answer

All daughters will have the disorder, but none of the sons will.

Question 16

Which of the following best explains why the frequency of recombinant offspring can be used to map the distance between genes?

Accepted Answer

The farther apart two genes are, the more likely crossing over will occur between them.

Question 17

Which of the following is NOT a feature of a model organism?

Accepted Answer

It is difficult to grow and has a long generation time.

Question 18

If a gene has more than two common alleles in a population, this is an example of:

Accepted Answer

Multiple allelism

Question 19

Which of the following crosses would you use to determine if a dominant phenotype is homozygous or heterozygous?

Accepted Answer

Testcross with a homozygous recessive individual

Question 20

Which of the following best describes the difference between sex-linkage and linkage?

Accepted Answer

Sex-linkage refers to genes on sex chromosomes, while linkage refers to genes on the same chromosome regardless of type.

Mendel and the Gene: Principles of Inheritance

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