downs syndrome is caused by

HESI LPN

HESI Maternal Newborn

1. What causes Down's syndrome?

A. Alcohol abuse by the mother at the time of conception.
B. Sex-linked chromosomal abnormalities.
C. An extra chromosome on the 21st pair.
D. Drug abuse by the mother during pregnancy.

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.

2. A woman gave birth to a 7-pound, 6-ounce infant girl 1 hour ago. The birth was vaginal and the estimated blood loss (EBL) was 1500 ml. When evaluating the woman’s vital signs, which finding would be of greatest concern to the nurse?

A. Temperature 37.9°C, heart rate 120 beats per minute (bpm), respirations 20 breaths per minute, and blood pressure 90/50 mm Hg.
B. Temperature 37.4°C, heart rate 88 bpm, respirations 36 breaths per minute, and blood pressure 126/68 mm Hg.
C. Temperature 38°C, heart rate 80 bpm, respirations 16 breaths per minute, and blood pressure 110/80 mm Hg.
D. Temperature 36.8°C, heart rate 60 bpm, respirations 18 breaths per minute, and blood pressure 140/90 mm Hg.

Correct answer: A

Rationale: An estimated blood loss (EBL) of 1500 ml following a vaginal birth is significant and can lead to hypovolemia. The vital signs provided in option A (Temperature 37.9°C, heart rate 120 bpm, respirations 20 breaths per minute, and blood pressure 90/50 mm Hg) indicate tachycardia and hypotension, which are concerning signs of hypovolemia due to excessive blood loss. Tachycardia is the body's compensatory mechanism to maintain cardiac output in response to decreased blood volume, and hypotension indicates inadequate perfusion. Options B, C, and D do not exhibit the same level of concern for hypovolemia. Option B shows tachypnea, which can be a result of pain or anxiety postpartum. Option C and D have vital signs within normal limits, which are not indicative of the body's response to significant blood loss.

3. What is the primary role of meiosis in the production of sperm and ova?

A. To reduce the chromosome number by half
B. To increase the chromosome number
C. To create identical copies of chromosomes
D. To repair damaged chromosomes

Correct answer: A

Rationale: The correct answer is A. Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of sperm and ova. Choice B is incorrect because meiosis does not increase the chromosome number. Choice C is incorrect because meiosis creates genetically diverse gametes, not identical copies of chromosomes. Choice D is incorrect because meiosis does not primarily function to repair damaged chromosomes.

4. If an individual receives a recessive gene for eye color from both parents, the:

A. gender of the child will not determine the expression of that trait.
B. recessive trait will be expressed in the child.
C. recessive trait will be expressed in all the offspring.
D. recessive trait will be suppressed, and the dominant trait will not be expressed.

Correct answer: B

Rationale: When an individual inherits a recessive gene for eye color from both parents, the recessive trait will be expressed in the child. This is because having two copies of the recessive gene overrides the presence of any dominant gene. Choice A is incorrect because the expression of the trait is determined by the genetic makeup, not the gender of the child. Choice C is incorrect as the expression of the recessive trait is certain when both parents pass on the recessive gene, but it does not mean that all offspring will express the trait. Choice D is incorrect because if both parents provide a recessive gene, the dominant trait will not be expressed in the child, but it does not mean it will be suppressed; rather, the recessive trait will be expressed.

5. What term is used to describe each member of a pair of genes?

A. allele
B. zygote
C. autosome
D. node

Correct answer: A

Rationale: The correct answer is 'allele.' An allele refers to one of two or more versions of a gene located at the same position on a chromosome. In genetics, alleles are responsible for variations in inherited traits. Choice B, 'zygote,' is incorrect as a zygote is a fertilized egg cell formed by the fusion of two gametes. Choice C, 'autosome,' is incorrect as autosomes are non-sex chromosomes that determine an individual's genetic traits excluding sex-linked characteristics. Choice D, 'node,' is incorrect as it does not relate to the concept of genes or genetic inheritance.