in the structure of deoxyribonucleic acid dna which of the following bases combines with thymine
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1. In the structure of deoxyribonucleic acid (DNA), which of the following bases combines with thymine?

Correct answer: B

Rationale: The correct answer is B: Adenine. In the structure of DNA, adenine pairs with thymine through hydrogen bonding, forming one of the complementary base pairs that make up the double helix structure of DNA. Cytosine pairs with guanine, not thymine. Rhodamine and serine are not DNA bases and do not participate in DNA base pairing. Therefore, choices A, C, and D are incorrect.

2. Preconception counseling is crucial for the safe management of diabetic pregnancies. Which complication is commonly associated with poor glycemic control before and during early pregnancy?

Correct answer: B

Rationale: Preconception counseling is essential as strict metabolic control before conception and in the early weeks of gestation helps reduce the risk of congenital anomalies. Frequent episodes of maternal hypoglycemia usually occur during the first trimester due to hormonal changes, affecting insulin production and use, rather than before conception. Hydramnios is more common in diabetic pregnancies, typically seen in the third trimester, not during early pregnancy. Hyperemesis gravidarum, although it may lead to hypoglycemic events, is related to decreased food intake and glucose transfer to the fetus, exacerbating hypoglycemia rather than being directly associated with poor glycemic control before and during early pregnancy.

3. During which of the following periods does the development of arms and legs occur in a pregnancy?

Correct answer: C

Rationale: The correct answer is C. The development of arms and legs occurs during the critical period of the fourth to eighth weeks of pregnancy. This timeframe is crucial for the formation of limbs and other key body parts. Choices A, B, and D are incorrect because the development of the lungs, heart, and stomach respectively occurs at different stages of fetal development and is not primarily associated with the fourth to eighth weeks of pregnancy.

4. Which procedure is used to detect neural tube defects such as spina bifida and certain chromosomal abnormalities?

Correct answer: D

Rationale: The correct answer is the Alpha-fetoprotein (AFP) assay. This blood test measures the level of AFP in a pregnant woman's blood, aiding in the detection of neural tube defects and certain chromosomal abnormalities in the fetus. Choice A, artificial insemination, is a method used to facilitate fertilization and is not related to detecting fetal abnormalities. Choice B, amniocentesis, involves collecting amniotic fluid for genetic testing, not directly measuring AFP levels. Choice C, endometriosis, is a medical condition involving abnormal tissue growth and is not a procedure for detecting fetal abnormalities. Therefore, the Alpha-fetoprotein (AFP) assay is the most appropriate option for detecting neural tube defects such as spina bifida and certain chromosomal abnormalities.

5. Is Duchenne muscular dystrophy a sex-linked abnormality?

Correct answer: A

Rationale: The correct answer is A: TRUE. Duchenne muscular dystrophy is an X-linked recessive disorder, primarily affecting males. This is due to the inheritance of the mutated gene on the X chromosome. Choices B, C, and D are incorrect because Duchenne muscular dystrophy is specifically classified as a sex-linked disorder affecting males due to the inheritance pattern.

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