Question 1

Which of the following best describes the difference between a gene and an allele?

Accepted Answer

A gene is a segment of DNA that codes for a trait, while an allele is a version of that gene.

Question 2

In pea plants, red flower colour (R) is dominant over white (r). If a heterozygous red-flowered plant (Rr) is crossed with a white-flowered plant (rr), what fraction of the offspring are expected to have white flowers? Use a Punnett square to justify your answer.

Accepted Answer

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

Question 3

Which genotype represents a homozygous recessive individual for flower colour in pea plants?

Accepted Answer

rr

Question 4

A pure-breeding red-flowered pea plant (RR) is crossed with a pure-breeding white-flowered pea plant (rr). What will be the genotype and phenotype of all F1 generation offspring?

Accepted Answer

Genotype: Rr; Phenotype: Red flowers

Question 5

Which of the following best explains why a recessive allele may not be expressed in the phenotype of an organism?

Accepted Answer

It is masked by the presence of a dominant allele.

Question 6

If two heterozygous pea plants (Rr) are crossed, what is the expected phenotypic ratio of red to white flowers in the F2 generation?

Accepted Answer

3:1

Question 7

Which of the following is an example of a sex-linked trait?

Accepted Answer

Colour-blindness

Question 8

A female who is heterozygous for colour-blindness (XNXn) marries a male with normal vision (XNY). What is the probability that their son will be colour-blind?

Accepted Answer

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

Question 9

Which chromosomal abnormality is associated with Down syndrome?

Accepted Answer

An extra chromosome 21 (trisomy 21)

Question 10

What is the genotype of a male with Klinefelter syndrome?

Accepted Answer

XXY

Question 11

Which of the following best describes a mutation?

Accepted Answer

A change in the base sequence of DNA

Question 12

Which type of mutation results in a protein that is incomplete and cannot function at all?

Accepted Answer

Nonsense mutation

Question 13

Which of the following agents is classified as a carcinogen?

Accepted Answer

UV light

Question 14

A frameshift mutation is caused by:

Accepted Answer

Insertion or deletion of one or more bases

Question 15

Which of the following best explains why males are more likely to be affected by X-linked recessive disorders?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will be expressed.

Question 16

If a woman with genotype XNXn (carrier for colour-blindness) and a man with genotype XnY (colour-blind) have children, what is the probability that a daughter will be colour-blind?

Accepted Answer

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

Question 17

Which of the following statements about pure-breeding is correct?

Accepted Answer

Pure-breeding results in offspring that are homozygous for a trait.

Question 18

Which of the following best describes the role of a Punnett square in genetics?

Accepted Answer

It predicts the probability of genotypes and phenotypes in offspring.

Question 19

Which of the following is a possible outcome of a missense mutation?

Accepted Answer

A single amino acid in the protein is changed, possibly altering protein function.

Question 20

A pedigree chart is useful for:

Accepted Answer

Tracing the inheritance of a genetic trait or disorder over generations.

Genetics and Inheritance: Patterns, Chromosomal Abnormalities, and Mutations

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