What determines a child's sex?

Correct Answer: D

Rationale: The correct answer is the sex chromosome received from the father. The father contributes either an X or Y chromosome, which determines the child's sex. This occurs at the moment of fertilization when the sperm carrying either an X (resulting in a female) or Y (resulting in a male) chromosome fertilizes the egg. Choices A, B, and C are incorrect because the presence of teratogens at the time of conception or ovulation does not determine the child's sex. While the sex chromosome received from the mother is important, it is the father's contribution that ultimately determines the child's sex.

Correct Answer: A

Rationale: Jill is a carrier of the recessive gene for Von Willebrand disease. Being a carrier means that she has one copy of the gene but does not show symptoms of the disease. Carriers can pass on the gene to their offspring. Choice B is incorrect as being a carrier does not mean she is susceptible to developing the disease after adolescence. Choice C is incorrect as 'acceptor' is not a term used in genetics in this context. Choice D is incorrect as susceptibility to the disease is not related to late adulthood in carriers of a recessive gene.

Correct Answer: A

Rationale: The correct characteristic of supermales, individuals with an XYY chromosome pattern, is that they are somewhat taller than average. Choice B is incorrect as supermales do not exhibit minimal facial hair growth compared to normal males. Choice C is incorrect as gynecomastia, the development of male breasts, is not a characteristic of supermales. Choice D is also incorrect as impotence is not a typical characteristic associated with supermales.

Correct Answer: C

Rationale: Tim's physical characteristics, such as narrow shoulders, low muscle mass, and lack of facial and body hair, are typical signs of Klinefelter syndrome, a genetic condition where males have an extra X chromosome (XXY). This leads to underdeveloped testes and reduced testosterone production, resulting in features like gynecomastia, sparse facial and body hair, and reduced muscle mass. Testosterone replacement therapy is commonly used to address the hormonal imbalance in individuals with Klinefelter syndrome. Phenylketonuria (PKU) is a metabolic disorder unrelated to the symptoms described in Tim's case. Cystic fibrosis is a genetic respiratory condition that does not present with the physical characteristics mentioned. Huntington's disease (HD) is a neurodegenerative disorder primarily affecting motor function and cognition, not physical appearance and muscle mass.

Correct Answer: C

Rationale: The correct answer is C. Sickle-cell anemia results from a mutation in the beta-globin gene, causing red blood cells to become sickle-shaped. These misshapen cells can obstruct small blood vessels, leading to reduced oxygen delivery to tissues. Choices A, B, and D are incorrect because sickle-cell anemia is typically managed with treatments such as pain relief medications, hydration, and in severe cases, blood transfusions. It is caused by a specific mutation in the beta-globin gene, not by the inability to metabolize phenylalanine. Additionally, sickle-cell anemia is more prevalent in individuals of African, Mediterranean, Middle Eastern, and Indian descent, not exclusive to any specific gender.