Consider statements about genetics: 1. DNA is double-stranded. 2. RNA is single-stranded. 3. DNA contains uracil. Which are correct? MCQ with Answer and Explanation

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Consider statements about genetics: 1. DNA is double-stranded. 2. RNA is single-stranded. 3. DNA contains uracil. Which are correct?

A. 2 and 3 only

B. 1 and 3 only

C. 1, 2 and 3

D. 1 and 2 only

Answer: Option D

Solution (By JKExamLibrary)

DNA (deoxyribonucleic acid) typically exists as a double-stranded helical molecule, with two complementary strands held together by hydrogen bonds between base pairs. RNA (ribonucleic acid) is generally single-stranded, allowing it to fold into complex three-dimensional shapes necessary for its various functions (mRNA, tRNA, rRNA). DNA contains the nitrogenous bases adenine, guanine, cytosine, and thymine; it does not contain uracil, which is found in RNA instead of thymine. Thus, statements 1 and 2 are correct.

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Question #1

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Consider statements about human nutrition: 1. Scurvy is caused by Vitamin D deficiency. 2. Anemia is often caused by iron deficiency. 3. Goiter is caused by iodine deficiency. Which are correct?

A. 2 and 3 only

B. 1 and 3 only

C. 1, 2 and 3

D. 1 and 2 only

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Correct Answer: Option A

Explanation:
Scurvy is caused by a deficiency of Vitamin C (ascorbic acid), leading to bleeding gums; rickets is caused by Vitamin D deficiency. Iron is essential for hemoglobin synthesis, and its deficiency leads to iron-deficiency anemia, causing fatigue and weakness. Iodine is required for thyroid hormone production, and its deficiency causes the enlargement of the thyroid gland, known as goiter. Thus, statements 2 and 3 are correct.

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Question #2

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Which of the following is a characteristic feature of cardiac muscle?

A. Branched fibres with intercalated discs

B. Spindle-shaped cells

C. Multinucleated syncytium

D. Voluntary control

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Correct Answer: Option A

Explanation:
Cardiac muscle cells are striated, branched, and connected by intercalated discs containing gap junctions for synchronized contraction. They are involuntary. Multinucleated syncytium is typical of skeletal muscle. Spindle-shaped non-striated cells characterize smooth muscle. Voluntary control is for skeletal muscle. Intercalated discs allow rapid ion passage, enabling the heart to function as a syncytium.

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Question #3

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Consider statements about cell biology: 1. The cell membrane is made of a phospholipid bilayer. 2. Ribosomes are the site of lipid synthesis. 3. The cytoskeleton provides structural support. Which are correct?

A. 1, 2 and 3

B. 1 and 3 only

C. 2 and 3 only

D. 1 and 2 only

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Correct Answer: Option B

Explanation:
The cell membrane (plasma membrane) is primarily composed of a phospholipid bilayer with embedded proteins, following the fluid mosaic model. The cytoskeleton is a network of protein filaments (microtubules, microfilaments, intermediate filaments) that provides structural support, shape, and facilitates intracellular transport. Ribosomes are the site of protein synthesis, not lipid synthesis (which occurs in the smooth ER). Thus, statements 1 and 3 are correct.

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