Question 1

Which of the following best describes the difference between autosomes and sex chromosomes in humans?

Accepted Answer

Autosomes are present in two copies in both sexes and are numbered, while sex chromosomes differ between males (XY) and females (XX).

Question 2

In the X-Y system of sex determination, which genotype would result in a biological male in humans?

Accepted Answer

$$XY$$

Question 3

A woman who is a carrier for red-green color blindness (an X-linked recessive trait) has children with a man who has normal color vision. What is the probability that their son will be color blind?

Accepted Answer

$$0.5$$

Question 4

Which of the following is an example of incomplete dominance?

Accepted Answer

A cross between a red-flowered plant ($$RR) $$and a white-flowered plant ($$rr) $$produces all pink-flowered offspring ($$Rr).$$

Question 5

In rabbits, the following alleles for coat color exist: $$C ($$full color) $$\u003e$$ $$c^{ch} ($$chinchilla) $$\u003e$$ $$c^h ($$himalayan) $$\u003e$$ $$c ($$albino). If a rabbit with genotype $$C c^h is $$crossed with a rabbit with genotype $$c^{ch} c$, which coat colors are possible in the offspring?

Accepted Answer

Full color, chinchilla, himalayan, and albino

Question 6

A Siamese cat has dark fur on its ears, paws, and tail due to a temperature-sensitive allele. What is the best explanation for this pattern?

Accepted Answer

The protein product of the allele is only functional at lower temperatures found in the extremities.

Question 7

Which of the following best describes codominance, as seen in human blood types?

Accepted Answer

Both alleles are expressed equally in the phenotype of the heterozygote.

Question 8

A genetic disease appears at an earlier age and with increased severity in each successive generation. This phenomenon is known as:

Accepted Answer

Genetic anticipation

Question 9

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causes defects in the lungs, pancreas, and sweat glands, as seen in cystic fibrosis.

Question 10

In a dihybrid cross involving two genes that interact epistatically, what is the expected phenotypic ratio in the F2 generation if one gene masks the effect of the other?

Accepted Answer

$$9:7$$

Question 11

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

Accepted Answer

A and B only

Question 12

Which of the following best explains incomplete penetrance?

Accepted Answer

The phenotype is not always expressed even when the genotype is present.

Question 13

A cross between two agouti mice with genotype $$AaBb$$ produces offspring with the following phenotypes: 9 agouti, 3 black, and 4 albino. Which genetic phenomenon explains the presence of albino mice?

Accepted Answer

Epistasis

Question 14

Which of the following is an example of a conditional allele?

Accepted Answer

An allele that causes a disease only when the individual consumes a specific nutrient, such as phenylalanine in PKU.

Question 15

Which of the following best describes a lethal allele?

Accepted Answer

An allele that causes death when present in the homozygous state.

Question 16

In sex-influenced inheritance, such as human pattern baldness, which statement is correct?

Accepted Answer

The trait is dominant in males but recessive in females.

Question 17

Which of the following is true about gene dosage effects?

Accepted Answer

Gene dosage effects often result in a stronger phenotype in homozygous females than in hemizygous males for X-linked genes.

Question 18

A pedigree shows a trait that skips generations and is seen mostly in males. What is the most likely mode of inheritance?

Accepted Answer

X-linked recessive

Question 19

Which of the following best describes the concept of expressivity?

Accepted Answer

The same genotype produces a range of phenotypes in different individuals.

Extensions of Mendelian Inheritance: Mechanisms and Examples

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