In the context of human reproduction, the 'Placenta' is fully formed and functional by the end of which trimester of pregnancy? MCQ with Answer and Explanation

Question

In the context of human reproduction, the 'Placenta' is fully formed and functional by the end of which trimester of pregnancy?

A. Third trimester (end of 36 weeks)

B. At the time of birth

C. First trimester (end of 12 weeks)

D. Second trimester (end of 24 weeks)

Answer: Option C

Solution (By JKExamLibrary)

The placenta begins to form immediately after implantation of the blastocyst. By the end of the first trimester (around 12 weeks of gestation), the placenta is fully formed and takes over the primary role of hormone production (progesterone and estrogen) from the corpus luteum. It is fully functional in providing oxygen, nutrients, and waste removal for the developing fetus for the remainder of the pregnancy. It is not fully formed at conception, nor does it wait until the second or third trimester.

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Question #1

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In a monohybrid cross between two heterozygous pea plants (Tt), the phenotypic ratio of tall to dwarf in the offspring is expected to be:

A. 1:1

B. 3:1

C. 9:3:3:1

D. 1:2:1

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Correct Answer: Option B

Explanation:
When both parents are heterozygous (Tt × Tt), the offspring genotypes are TT (25%), Tt (50%), and tt (25%). Since tall (T) is dominant over dwarf (t), both TT and Tt are tall, resulting in 3 tall : 1 dwarf phenotypic ratio. The genotypic ratio is 1:2:1. 9:3:3:1 is the dihybrid phenotypic ratio. 1:1 ratio is seen in test cross (Tt × tt).

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Question #2

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The respiratory pigment hemocyanin contains which metal?

A. Zinc

B. Copper

C. Magnesium

D. Iron

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Correct Answer: Option B

Explanation:
Hemocyanin is a blue, copper-containing respiratory pigment found in the hemolymph of some mollusks and arthropods. It binds oxygen reversibly. Hemoglobin contains iron and is red. Magnesium is in chlorophyll, zinc in some enzymes. Hemocyanin is not bound to cells but floats freely in hemolymph.

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Question #3

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Which of the following is a saturated fatty acid?

A. Linoleic acid

B. Palmitic acid

C. Linolenic acid

D. Oleic acid

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Correct Answer: Option B

Explanation:
Saturated fatty acids have no double bonds between the carbon atoms in their hydrocarbon chain, making them 'saturated' with hydrogen atoms. They are typically solid at room temperature. Palmitic acid and stearic acid are common saturated fats. Oleic, linoleic, and linolenic acids are unsaturated fatty acids, containing one or more double bonds.

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