Question 1

Which of the following best explains why individuals with Klinefelter syndrome (47,XXY) develop male characteristics despite having two X chromosomes?

Accepted Answer

The presence of the Y chromosome, specifically the SRY gene, triggers male development.

Question 2

In Drosophila melanogaster, what is the expected sexual phenotype of an individual with a karyotype of $$2X:3A ($$two X chromosomes and three sets of autosomes)?

Accepted Answer

Intersex

Question 3

Which of the following statements about dosage compensation in mammals is correct?

Accepted Answer

Dosage compensation equalizes the expression of X-linked genes between males and females by inactivating one X chromosome in females.

Question 4

A female calico cat displays patches of black and orange fur. Which genetic mechanism best explains this pattern?

Accepted Answer

Random X-chromosome inactivation (Lyon hypothesis) in heterozygous females.

Question 5

Which of the following karyotypes would you expect to find two Barr bodies in a human somatic cell?

Accepted Answer

47,XXX

Question 6

A geneticist observes a human with the following characteristics: short stature, webbed neck, underdeveloped breasts, and a karyotype of 45 chromosomes. Which condition is most likely present?

Accepted Answer

Turner syndrome (45,X)

Question 7

Which gene is critical for initiating male sexual development in humans, and on which chromosome is it located?

Accepted Answer

SRY gene on the Y chromosome

Question 8

In reptiles with temperature-dependent sex determination (TSD), which enzyme is directly affected by temperature and plays a key role in determining sex?

Accepted Answer

Aromatase

Question 9

A human cell is found to have no Barr bodies. Which of the following karyotypes is most consistent with this observation?

Accepted Answer

45,X (Turner syndrome)

Question 10

Which of the following best describes the function of the pseudoautosomal regions (PAR) on the Y chromosome?

Accepted Answer

They allow pairing and recombination with the X chromosome during meiosis.

Question 11

A Drosophila with a karyotype of $$3X:2A is $$observed. What is the expected sexual phenotype?

Accepted Answer

Metafemale

Question 12

Which of the following is a plausible explanation for why individuals with Turner syndrome (45,X) are not phenotypically normal, despite X-inactivation?

Accepted Answer

Some genes on the X chromosome escape inactivation and require two copies for normal development.

Question 13

Which of the following best describes the Lyon hypothesis?

Accepted Answer

X-chromosome inactivation is random in each cell, and all descendant cells maintain the same inactivation pattern.

Question 14

In C. elegans, which of the following karyotypes would result in a male phenotype?

Accepted Answer

XO (one X chromosome, no Y)

Question 15

A human male is found to have a karyotype of 47,XYY. Which of the following characteristics is most consistently associated with this condition?

Accepted Answer

Increased height (over 6 feet tall)

Question 16

Which of the following statements about the X-inactivation center (Xic) is correct?

Accepted Answer

It contains the XIST gene, which is critical for X-chromosome inactivation.

Question 17

Which of the following best explains why a female with a 47,XXX karyotype may be phenotypically normal?

Accepted Answer

All but one X chromosome are inactivated, preventing excess gene expression.

Question 18

Which of the following is true regarding sex determination in Drosophila melanogaster?

Accepted Answer

Sex is determined by the ratio of X chromosomes to sets of autosomes.

Question 19

A reptile species exhibits 100% female offspring at low and high incubation temperatures, but a mix of males and females at intermediate temperatures. Which TSD pattern does this represent?

Accepted Answer

Case III

Question 20

Which of the following best describes genomic imprinting as it relates to X-chromosome inactivation?

Accepted Answer

It is the process by which only one homolog's genes are expressed, while the other is silenced.

Lecture slides Chapter 5

Study Guide - Practice Questions

Study Guide - Flashcards