Q: Which equation correctly represents the X:A ratio that determines sex in Drosophila melanogaster?

$$\text{X:A ratio} = \frac{\text{Number of X chromosomes}}{\text{Number of sets of autosomes}}$$

Question 1

Which gene is primarily responsible for initiating male development in human embryos?

Accepted Answer

SRY

Question 2

In mammals, what is the chromosomal composition of a typical female?

Accepted Answer

XX

Question 3

A patient presents with tall stature, small testicles, gynecomastia, and mild learning disabilities. Karyotype analysis reveals 47,XXY. What is the most likely diagnosis?

Accepted Answer

Klinefelter syndrome

Question 4

Which of the following best describes dosage compensation in mammals?

Accepted Answer

All but one X chromosome are inactivated in each somatic cell of females.

Question 5

In birds, which sex is heterogametic and what is their chromosomal composition?

Accepted Answer

Females; ZW

Question 6

A female patient is found to have a 45,X karyotype. Which syndrome does she most likely have, and what is a common symptom?

Accepted Answer

Turner syndrome; short stature

Question 7

Which equation correctly represents the X:A ratio that determines sex in Drosophila melanogaster?

Accepted Answer

$$	ext{X:A ratio} = \frac{	ext{Number of X chromosomes}}{	ext{Number of sets of autosomes}}$$

Question 8

Which of the following is TRUE regarding the Lyon Hypothesis?

Accepted Answer

X chromosome inactivation occurs randomly in somatic cells early in embryonic development.

Question 9

A karyotype of 47,XXX is most likely associated with which of the following symptoms?

Accepted Answer

Taller than average and mild developmental delays

Question 10

Which gene is essential for X chromosome inactivation in mammals?

Accepted Answer

XIST

Question 11

In the XO sex determination system found in grasshoppers, what is the chromosomal composition of males?

Accepted Answer

XO

Question 12

Which of the following disorders is characterized by genetic males (XY) who are insensitive to androgens and develop female characteristics?

Accepted Answer

Androgen Insensitivity Syndrome (AIS)

Question 13

If a human has a karyotype of 48,XXXY, how many Barr bodies would you expect to find in their somatic cells?

Accepted Answer

$$2$$

Question 14

Which of the following best explains why sex chromosome variants (such as XXY or XO) show phenotypic effects despite dosage compensation?

Accepted Answer

Some genes on the X chromosome escape inactivation and are expressed from both X chromosomes.

Question 15

A turtle species exhibits temperature-dependent sex determination. Which type of sex determination system does this represent?

Accepted Answer

Environmental Sex Determination (ESD)

Question 16

Which of the following karyotypes would NOT be expected to have any Barr bodies?

Accepted Answer

45,X

Question 17

In humans, which parent determines the sex of the offspring and why?

Accepted Answer

Father, because sperm can be X or Y

Question 18

Which of the following is TRUE about the ZW sex determination system?

Accepted Answer

Females are heterogametic (ZW)

Question 19

A male with a karyotype of 47,XYY is most likely to exhibit which of the following characteristics?

Accepted Answer

Taller than average and mild learning disabilities

Question 20

Which process ensures that gene expression from X-linked genes is balanced between males and females in mammals?

Accepted Answer

Dosage compensation via X chromosome inactivation

Sex Determination and Sex Chromosomes: Mechanisms, Systems, and Disorders

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