Question 1

Which of the following karyotypes is associated with Turner Syndrome, and what is the most common physical feature observed in individuals with this condition?

Accepted Answer

45,X; Short stature

Question 2

A male patient presents with tall stature, gynecomastia, small testes, and infertility. Karyotyping reveals an extra X chromosome. What is the most likely diagnosis and the karyotype?

Accepted Answer

Klinefelter Syndrome; 47,XXY

Question 3

Which gene is responsible for initiating testicular development in embryos, and where is it located?

Accepted Answer

SRY gene on the short arm of the Y chromosome

Question 4

What is the primary reason why individuals with sex chromosome aneuploidies (except complete absence of an X chromosome in males) are often compatible with survival?

Accepted Answer

X-chromosome inactivation reduces the impact of extra X chromosomes

Question 5

A 47,XYY male is most likely to present with which of the following clinical features?

Accepted Answer

Tall stature and normal sexual development

Question 6

Which of the following best explains the origin of the extra X chromosome in Klinefelter Syndrome?

Accepted Answer

Nondisjunction during meiosis I or II in either parent

Question 7

A female patient with a 47,XXX karyotype is most likely to have which of the following outcomes?

Accepted Answer

Usually benign clinical features due to X-chromosome inactivation

Question 8

Which equation correctly represents the probability of a live birth with Turner Syndrome, given the karyotype 45,X is estimated to occur in 1-2% of conceptions but only 1/2000 to 1/4000 live-born females?

Accepted Answer

$$P_{live} = \frac{1}{2000} to$$ $$\frac{1}{4000}$$

Question 9

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

Accepted Answer

SRY gene encodes a transcription factor that initiates male sex determination

Question 10

A child is born with ambiguous genitalia and karyotyping reveals 46,XX with a translocation of the SRY gene onto one X chromosome. What is the most likely explanation for this phenotype?

Accepted Answer

SRY gene translocation onto the X chromosome causing sex reversal

Question 11

Which of the following is a common clinical feature of Turner Syndrome (45,X) but not of Klinefelter Syndrome (47,XXY)?

Accepted Answer

Short stature

Question 12

What is the most reliable method for diagnosing Klinefelter Syndrome?

Accepted Answer

Karyotyping to detect 47,XXY

Question 13

Which of the following best describes the function of the SRY gene product?

Accepted Answer

It is a DNA bending transcription factor that promotes testis formation

Question 14

During meiosis in males, crossing over can occur between the tip of the X chromosome and the tip of the Y chromosome. What is this region called?

Accepted Answer

Pseudoautosomal region

Question 15

Which of the following is TRUE regarding the frequency of major sex chromosome aneuploidies?

Accepted Answer

47,XXY occurs in approximately 1/1,000 males

Question 16

A patient with 47,XYY syndrome is most likely to have which of the following outcomes?

Accepted Answer

Normal sexual development and may be unaware of the extra Y chromosome

Question 17

Which of the following best explains why most cases of Trisomy X (47,XXX) are clinically benign?

Accepted Answer

X-chromosome inactivation ensures only one X is active

Question 18

A mutation in the SRY gene can result in which of the following scenarios?

Accepted Answer

A female with 46,XY karyotype and gonadal dysgenesis

Question 19

Which of the following is a distinguishing feature of Klinefelter Syndrome compared to other sex chromosome aneuploidies?

Accepted Answer

Presence of an extra X chromosome in males (47,XXY)

Sex Chromosome Abnormalities and Sex Determination in Humans

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