$$1 \text{ male} : 1 \text{ female}$$

Question 1

Which gene is primarily responsible for initiating male sexual development in humans, and what is its main function?

Accepted Answer

SRY; it directs the bipotential gonad to develop into testes.

Question 2

A person with an XY karyotype has a mutation in the AR gene resulting in a non-functional androgen receptor. What is the most likely phenotype?

Accepted Answer

Female external characteristics and sterility.

Question 3

Which of the following best describes dosage compensation in humans?

Accepted Answer

One X chromosome is randomly inactivated in each cell of females.

Question 4

In the ZZ/ZW sex determination system, which sex is heterogametic and in which organisms is this system commonly found?

Accepted Answer

Females are heterogametic; found in birds and some fish.

Question 5

A mutation in the SRD5A2 gene prevents the conversion of testosterone to DHT in an XY individual. What is the expected outcome?

Accepted Answer

Male internal genitalia but ambiguous or female-like external genitalia.

Question 6

Which of the following is true about the haplodiploidy sex determination system, as seen in bees?

Accepted Answer

Males are haploid and develop from unfertilized eggs.

Question 7

Which process is responsible for sperm production in haploid male bees?

Accepted Answer

Mitosis, because there are no homologous pairs to separate.

Question 8

A tortoiseshell cat displays patches of orange and black fur. What genetic mechanism explains this pattern?

Accepted Answer

Random inactivation of one X chromosome in each cell.

Question 9

Which of the following is a holandric trait?

Accepted Answer

A trait encoded by a gene on the Y chromosome outside the PAR.

Question 10

In humans, what is the expected primary sex ratio at conception under normal circumstances?

Accepted Answer

$$1 	ext{ male} : 1 	ext{ female}$$

Question 11

Which of the following best describes the role of SOX9 in human sexual development?

Accepted Answer

It is a transcription factor activated by SRY that promotes testis development.

Question 12

Which of the following is NOT a type of genetic sex determination system?

Accepted Answer

Temperature-dependent sex determination

Question 13

A grasshopper has an X0 sex determination system. What is the chromosomal composition of a male grasshopper?

Accepted Answer

X

Question 14

Which of the following scenarios would most likely result in an individual with both male and female secondary sexual characteristics?

Accepted Answer

A mutation in the CYP21 gene causing excess androgen production.

Question 15

Which of the following statements about the pseudoautosomal regions (PARs) of sex chromosomes is correct?

Accepted Answer

PARs are regions of sequence similarity where X and Y chromosomes pair during meiosis.

Question 16

Which of the following best explains why environmental sex determination is common in reptiles?

Accepted Answer

Sex chromosomes are absent, and temperature during development determines sex.

Question 17

If a human embryo is XX but has a translocated SRY gene on one X chromosome, what is the most likely outcome?

Accepted Answer

The embryo will develop as a typical male.

Question 18

Which of the following is a real-world example of dosage compensation in mammals?

Accepted Answer

Random X inactivation in female mammals, leading to mosaic phenotypes such as tortoiseshell cats.

Question 19

Which of the following statements about the SRY gene is FALSE?

Accepted Answer

SRY is sufficient by itself for complete male sexual development.

Question 20

Which of the following best describes the difference between sex and gender?

Accepted Answer

Sex refers to biological characteristics, while gender refers to identity and social roles.

Sex Determination and Dosage Compensation in Genetics

Study Guide - Practice Questions