Question 1

Which of the following best explains why Mendel chose the garden pea (Pisum sativum) as his model organism for studying inheritance?

Accepted Answer

Pea plants are inexpensive, easy to grow, have a short generation time, and produce many offspring, making them ideal for genetic studies.

Question 2

A scientist crosses two true-breeding pea plants, one with round seeds (RR) and one with wrinkled seeds (rr). All F1 offspring have round seeds. Which hypothesis does this result support?

Accepted Answer

Particulate inheritance, because the traits do not blend and the genetic determinants remain discrete.

Question 3

In a monohybrid cross between two heterozygous pea plants (Rr × Rr), what is the expected phenotypic ratio of round to wrinkled seeds in the F2 generation?

Accepted Answer

$$3:1$$

Question 4

Which of the following statements about dominant and recessive alleles is correct?

Accepted Answer

Dominant alleles mask the expression of recessive alleles in heterozygotes, but this does not imply anything about their frequency or fitness.

Question 5

A dihybrid cross is performed between two heterozygous pea plants (RrYy × RrYy), where R = round, r = wrinkled, Y = yellow, y = green. What is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 6

Which of the following best describes the principle of independent assortment?

Accepted Answer

Alleles of different genes assort independently of one another during meiosis if they are on different chromosomes.

Question 7

A woman who is a carrier for an X-linked recessive trait (X	extsuperscript{N}X	extsuperscript{n}) and a man who does not have the trait (X	extsuperscript{N}Y) have children. What is the probability that a son will express the trait?

Accepted Answer

$$1/2$$

Question 8

Which scenario below is an example of incomplete dominance?

Accepted Answer

A cross between red-flowered and white-flowered four o’clock plants produces all pink-flowered offspring.

Question 9

Which of the following best explains why linked genes do not always show perfect linkage in offspring?

Accepted Answer

Crossing over during meiosis can separate linked genes, resulting in recombinant offspring.

Question 10

A pedigree shows a trait that appears equally in males and females, skips generations, and affected individuals often have unaffected parents. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 11

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causes both long limbs and heart defects in Marfan syndrome.

Question 12

If a gene has three alleles (I	extsuperscript{A}, I	extsuperscript{B}, i) for blood type, how many possible genotypes can exist for this gene in humans?

Accepted Answer

$$6$$

Question 13

A testcross is performed between a plant with an unknown genotype showing the dominant phenotype and a homozygous recessive plant. If the unknown plant is heterozygous, what is the expected ratio of phenotypes in the offspring?

Accepted Answer

$$1:1$$

Question 14

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes each contribute a small effect to a single trait, resulting in continuous variation.

Question 15

In a cross between AaBb and aabb individuals, assuming independent assortment, what proportion of the offspring are expected to be AaBb?

Accepted Answer

$$1/4$$

Question 16

Which of the following is true regarding the chromosomal theory of inheritance?

Accepted Answer

Genes are located on chromosomes, and the behavior of chromosomes during meiosis explains Mendel's principles.

Question 17

A woman with type AB blood and a man with type O blood have children. What are the possible blood types of their children?

Accepted Answer

Type A or type B

Question 18

Which of the following best explains why environmental factors can influence phenotype?

Accepted Answer

The phenotype is often the result of both genotype and environmental influences, as seen in PKU where diet can prevent symptoms.

Question 19

If two genes are 10 centiMorgans (cM) apart on the same chromosome, what percentage of recombinant offspring would you expect from a cross involving these genes?

Accepted Answer

$$10\%$$

Question 20

A pedigree shows that all daughters of an affected male are affected, but none of his sons are. What is the most likely mode of inheritance?

Accepted Answer

X-linked dominant

Mendel and the Gene: Principles of Inheritance

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