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

Consider statements about genetics: 1. DNA is double-stranded. 2. RNA is single-stranded. 3. DNA contains uracil. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 3 only
Answer: Option A
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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Practice More Biology Questions

Question #1
Assertion (A): Water is essential for photosynthesis.
Reason (R): Water is split to release oxygen, and its hydrogen is used to reduce CO₂.
A. A false, R true.
B. Both A and R are true, but R is not the correct explanation.
C. Both A and R are true, and R is the correct explanation.
D. A true, R false.

Correct Answer: Option C


Explanation:
Photolysis of water provides electrons and protons for the light reactions, releasing O₂; NADPH formed carries hydrogen to reduce CO₂ in the Calvin cycle. R correctly explains A.

This question belongs to: Science Biology
Question #2
The hormone that stimulates the kidney to reabsorb sodium and water, increasing blood pressure, is:
A. ADH
B. Aldosterone
C. Renin
D. ANP

Correct Answer: Option B


Explanation:
Aldosterone, from the adrenal cortex, acts on the distal tubule and collecting duct to increase sodium reabsorption (and water follows) and potassium secretion, raising blood volume and pressure. ADH increases water reabsorption, ANP reduces sodium reabsorption, renin is an enzyme initiating the RAAS.

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Question #3
The part of the seed that contains stored food for the embryo is the:
A. Cotyledon
B. Seed coat
C. Plumule
D. Radicle

Correct Answer: Option A


Explanation:
Cotyledons are seed leaves that store food (starch, proteins, lipids) for the developing embryo and may become photosynthetic after germination. Monocots have one, dicots two. Radicle is root, plumule shoot, seed coat protects.

This question belongs to: Science Biology