What is the typical sex chromosome pattern for females?

Correct Answer: A

Rationale: The typical sex chromosome pattern for females is XX. Females have two X chromosomes, which is represented as XX. Choice B (XYY) is incorrect as it represents the sex chromosome pattern for males with an extra Y chromosome. Choice C (XY) is the sex chromosome pattern for males. Choice D (XXY) represents a genetic disorder known as Klinefelter syndrome, where males have an extra X chromosome.

Correct Answer: C

Rationale: Down's syndrome, also known as trisomy 21, is caused by the presence of an extra chromosome on the 21st pair. Choice A is incorrect as alcohol abuse is not the cause of Down's syndrome. Choice B is incorrect because Down's syndrome is not related to sex-linked chromosomal abnormalities. Choice D is also incorrect as drug abuse by the mother during pregnancy is not the cause of Down's syndrome.

Correct Answer: C

Rationale: Individuals with Klinefelter syndrome have an extra X chromosome (XXY) and typically have reduced testosterone levels, which can lead to gynecomastia (enlarged breasts). This condition is not usually associated with Down syndrome (choice A), XYY syndrome (choice B), or Turner syndrome (choice D), making them less likely to have gynecomastia.

Correct Answer: C

Rationale: Daisy's symptoms of short stature and infertility, along with the prescription of estrogen replacement therapy, are indicative of Turner syndrome. Turner syndrome is a genetic condition in which a female is partially or completely missing one X chromosome. This results in short stature, infertility, and other physical characteristics. Phenylketonuria (PKU) is a metabolic disorder caused by a mutation in the gene responsible for the breakdown of the amino acid phenylalanine. Cystic fibrosis is a genetic disorder affecting the respiratory and digestive systems. Huntington's disease (HD) is a neurodegenerative disorder that affects muscle coordination and leads to cognitive decline.

Correct Answer: A

Rationale: Tay-Sachs disease is a genetic disorder that causes a progressive degeneration of the central nervous system, particularly in infants. Choice B, Cystic fibrosis, is a genetic disorder that primarily affects the lungs and digestive system, not the central nervous system. Choices C and D, Turner syndrome and Klinefelter syndrome, are chromosomal disorders that do not directly involve degeneration of the central nervous system.