Question 1

Which of the following best describes the mechanism of sex determination in Protenor insects?

Accepted Answer

Males are heterogametic (X 0), producing gametes with or without the X chromosome, and the presence or absence of X determines offspring sex.

Question 2

A human karyotype reveals 47 chromosomes, including two X chromosomes and one Y chromosome. Which syndrome is most likely present, and what is a typical phenotype?

Accepted Answer

Klinefelter syndrome; tall stature, rudimentary testes, and slight breast enlargement.

Question 3

Which gene is responsible for triggering the development of testes in human embryos, and what is its encoded protein called?

Accepted Answer

SRY gene; encodes the testis-determining factor (TDF).

Question 4

In mammals, dosage compensation is achieved by inactivating one X chromosome in females. According to the Lyon hypothesis, what is the expected number of Barr bodies in a cell from a female with a 47,XXX karyotype?

Accepted Answer

2

Question 5

Which of the following statements about the Y chromosome is correct?

Accepted Answer

Pseudoautosomal regions (PARs) on the Y chromosome allow recombination with the X chromosome during meiosis.

Question 6

A female calico cat displays patches of black and orange fur. Which genetic principle does this illustrate?

Accepted Answer

Random X chromosome inactivation as described by the Lyon hypothesis.

Question 7

If a human embryo has a 45,X karyotype, which syndrome is present and what is the most likely outcome regarding gonadal development?

Accepted Answer

Turner syndrome; rudimentary ovaries and female external genitalia.

Question 8

Which equation correctly represents the number of Barr bodies in a cell, given $$N X $$chromosomes?

Accepted Answer

$$N - 1$$

Question 9

Which of the following best explains why individuals with Turner syndrome (45,X) are not entirely normal despite X-inactivation mechanisms?

Accepted Answer

X-inactivation does not occur in early gonadal development, and not all X-linked genes are inactivated.

Question 10

Which ethical concern is most directly associated with non-medical sex selection via preimplantation genetic testing (PGT)?

Accepted Answer

Reinforcement of gender bias and social inequality.

Question 11

A couple uses PGT-A to select embryos for transfer based on sex. Which technique is most likely used to determine the chromosomal composition of the embryos?

Accepted Answer

Next-generation sequencing or array comparative genomic hybridization.

Question 12

Which of the following is a potential societal consequence of widespread non-medical sex selection?

Accepted Answer

Increased risk of forced marriage and human trafficking due to demographic imbalances.

Question 13

In a population where males are the heterogametic sex (X Y), what is the expected ratio of X-bearing to Y-bearing sperm produced?

Accepted Answer

1:1

Question 14

Which of the following best describes the function of the X-inactivation center (Xic) and the XIST gene?

Accepted Answer

Xic is a control unit on the X chromosome; XIST gene is expressed on the inactivated X and is critical for X-inactivation.

Question 15

A male with a 47,X Y Y karyotype is most likely to exhibit which characteristic?

Accepted Answer

Tall stature and possible personality disorders.

Question 16

Which regulatory approach is most commonly used in the United Kingdom and Canada regarding sex selection via PGT?

Accepted Answer

Strict medical restrictions, allowing sex selection mainly to prevent serious sex-linked genetic disorders.

Question 17

Which of the following best explains why the secondary sex ratio in humans is not exactly 1.0?

Accepted Answer

Factors affecting fetal mortality and survival rates may skew the ratio of males to females born.

Question 18

Which real-world scenario best illustrates the ethical risks of sex selection technologies?

Accepted Answer

A country experiences a skewed sex ratio, leading to increased human trafficking and forced marriage.

Question 19

Which of the following is true regarding mosaicism in individuals with sex chromosome abnormalities?

Accepted Answer

Mosaic individuals display two or more genetic cell lines with different karyotypes.

Sex Determination and Sex Chromosomes: Mechanisms, Disorders, and Ethical Implications

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