Which base is found in RNA but not in DNA? MCQ with Answer and Explanation

Which base is found in RNA but not in DNA?
A. Uracil
B. Adenine
C. Guanine
D. Thymine
Answer: Option A
Solution (By JKSSB Mock Tests)
Uracil replaces thymine in RNA. In DNA, thymine pairs with adenine; in RNA, uracil pairs with adenine. Adenine, guanine, and cytosine are present in both. The presence of uracil and the sugar ribose (vs. deoxyribose) are key structural differences between RNA and DNA.

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Practice More Biology Questions

Question #1
The process of movement of water from a hypotonic solution to a hypertonic solution across a semipermeable membrane is:
A. Active transport
B. Osmosis
C. Diffusion
D. Facilitated diffusion

Correct Answer: Option B


Explanation:
Osmosis is the net diffusion of water through a selectively permeable membrane from a region of low solute (high water potential) to high solute (low water potential).

This question belongs to: Science Biology
Question #2
Consider the following statements about the human heart:
1. The right atrium receives blood from the vena cavae.
2. The left ventricle pumps blood to the lungs.
3. The septum separates the left and right sides.
Which of the above is/are correct?
A. 2 and 3 only
B. 1, 2, and 3
C. 1 and 2 only
D. 1 and 3 only

Correct Answer: Option D


Explanation:
The right atrium receives deoxygenated blood; the left ventricle pumps to the body (not lungs). Septum divides the heart. So 2 is incorrect.

This question belongs to: Science Biology
Question #3
Diphtheria is a bacterial disease caused by:
A. Bacillus anthracis
B. Corynebacterium diphtheriae
C. Clostridium tetani
D. Haemophilus influenzae

Correct Answer: Option B


Explanation:
Diphtheria is a highly contagious bacterial infection caused by Corynebacterium diphtheriae. It primarily affects the mucous membranes of the nose and throat, producing a thick gray pseudomembrane. The bacteria also produce a potent exotoxin that can damage the heart, kidneys, and nervous system. It is preventable by the DPT vaccine.

This question belongs to: Science Biology