dizygotic dz twins share percent of their genes
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HESI Focus on Maternity Exam

1. Dizygotic (DZ) twins share _________ percent of their genes.

Correct answer: C

Rationale: Dizygotic (DZ) twins share approximately 50% of their genes. This is because dizygotic twins, also known as fraternal twins, originate from two separate fertilized eggs and share similar genetic similarity to regular siblings. Choice A (100%) is incorrect because if twins shared 100% of their genes, they would be identical twins (monozygotic). Choice B (75%) is incorrect as it is not the typical genetic similarity seen in dizygotic twins. Choice D (25%) is incorrect as it represents a significantly lower genetic similarity than what is observed in dizygotic twins.

2. After meiosis, each new cell nucleus contains _____ chromosomes.

Correct answer: C

Rationale: After meiosis, each resulting cell contains 23 chromosomes. Meiosis is a process that involves two sequential divisions resulting in four daughter cells, each with half the number of chromosomes as the parent cell. In humans, the parent cell has 46 chromosomes (diploid), and after meiosis, the resulting cells (sperm or ova) have 23 chromosomes (haploid). Choice A (46 chromosomes) is incorrect because this is the number of chromosomes in a human diploid cell before meiosis. Choices B (35 chromosomes) and D (12 chromosomes) are incorrect as they do not represent the correct number of chromosomes after meiosis in human cells.

3. What is the process in which the double helix of deoxyribonucleic acid (DNA) duplicates?

Correct answer: B

Rationale: Mitosis is the correct answer because it is the process of cell division in which a cell duplicates its DNA and divides into two identical daughter cells. During mitosis, the DNA is replicated, and each daughter cell receives an identical copy of the genetic material. Amniocentesis is a medical procedure to collect amniotic fluid for prenatal genetic testing and is not related to DNA duplication. Meiosis is a type of cell division that produces gametes with half the genetic material of the parent cell, leading to genetic diversity. Mutation is a permanent alteration in the DNA sequence that can lead to genetic variations but is not the process of DNA duplication.

4. What causes Down's syndrome?

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.

5. A newborn with a respiratory rate of 40 breaths per minute at one minute after birth is demonstrating cyanosis of the hands and feet. What action should a nurse take?

Correct answer: B

Rationale: Cyanosis of the hands and feet, known as acrocyanosis, is common in newborns shortly after birth and usually resolves on its own. It is not indicative of a need for immediate intervention. Therefore, the appropriate action is to continue monitoring the newborn's condition. Assessing bowel sounds (Choice A) is not relevant to the presenting issue of cyanosis and respiratory rate. Assisting with intubation (Choice C) is an invasive procedure that is not warranted based on the information provided. Rubbing the infant's back (Choice D) is not necessary for acrocyanosis and could potentially disturb the newborn.

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