Nursing Elites

1. Twins that derive from a single zygote that has split into two are called:

• A. monozygotic (MZ) twins.
• B. fraternal twins.
• C. non-identical twins.
• D. dizygotic (DZ) twins.

Correct answer: A

Rationale: The correct answer is A: monozygotic (MZ) twins. Monozygotic twins, also known as identical twins, occur when a single zygote splits into two embryos, leading to two genetically identical individuals. Choice B, fraternal twins, are twins that develop from two separate eggs fertilized by two different sperm cells, resulting in non-identical siblings. Choice C, non-identical twins, is not a common term used to describe this type of twinning. Choice D, dizygotic (DZ) twins, refer to twins that develop from two separate eggs fertilized by two different sperm cells, leading to non-identical twins.

2. Which of the following statements is true of Down’s syndrome?

• A. Down’s syndrome is usually caused by an extra copy of chromosome 21 in an individual.
• B. The symptoms of Down’s syndrome are similar to those of sickle-cell anemia.
• C. Down’s syndrome is caused by a sexually transmitted infection (STI) during conception.
• D. The probability of having a child with Down’s syndrome increases with the age of the parents.

Correct answer: D

Rationale: The correct answer is D. The likelihood of having a child with Down’s syndrome increases as the age of the parents increases, particularly the mother's age. Choice A is incorrect because Down’s syndrome is caused by an extra copy of chromosome 21, not a defect in the sex chromosomes. Choice B is incorrect as the symptoms of Down’s syndrome and sickle-cell anemia are different. Choice C is also incorrect as Down’s syndrome is not caused by a sexually transmitted infection during conception.

3. _____ are environmental agents that can harm the embryo or fetus.

• A. Mutations
• B. Autosomes
• C. Teratogens
• D. Androgens

Correct answer: C

Rationale: Teratogens are environmental agents, such as drugs, chemicals, or infections, that can cause harm to a developing embryo or fetus. Mutations (Choice A) refer to changes in the DNA sequence and are not environmental agents. Autosomes (Choice B) are chromosomes that are not involved in determining an individual's sex and are not environmental agents that harm the embryo or fetus. Androgens (Choice D) are a group of hormones that are more related to male sexual development and function, not environmental agents that harm the embryo or fetus.

4. According to a study in 2014 by Skakkebaek et al., who among the following is most likely to have gynecomastia?

• A. Jennifer, a dancer, who has Down syndrome
• B. Frank, a teacher, who is diagnosed with XYY syndrome
• C. Peter, a fashion designer, who has Klinefelter syndrome
• D. Ria, a gym instructor, who is diagnosed with Turner 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.

5. What determines a child’s sex?

• A. Presence of teratogens at the time of conception.
• B. Sex chromosome received from the mother.
• C. Presence of teratogens at the time of ovulation.
• D. Sex chromosome received from the father.

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.

Similar Questions