The nucleolus within the nucleus is the site of synthesis for which cellular component? MCQ with Answer and Explanation

The nucleolus within the nucleus is the site of synthesis for which cellular component?
A. Lipids
B. mRNA
C. DNA
D. rRNA and ribosome assembly
Answer: Option D
Solution (By JKSSB Mock Tests)
The nucleolus is a prominent, non-membrane-bound structure within the nucleus. It is the site of active ribosomal RNA (rRNA) synthesis and the assembly of ribosomal subunits. These subunits then exit the nucleus through nuclear pores to combine in the cytoplasm and form functional ribosomes for protein synthesis.

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Practice More Biology Questions

Question #1
The antibiotic that inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit is:
A. Cephalosporin
B. Penicillin
C. Tetracycline
D. Vancomycin

Correct Answer: Option C


Explanation:
Tetracycline binds to the 30S ribosomal subunit, blocking attachment of aminoacyl-tRNA, thus inhibiting protein synthesis. Penicillin and cephalosporins inhibit cell wall synthesis, vancomycin also inhibits cell wall synthesis. Aminoglycosides like streptomycin also target 30S. Protein synthesis inhibitors exploit the difference between bacterial and human ribosomes.

This question belongs to: Science Biology
Question #2
Assertion (A): Frogs have a three-chambered heart.
Reason (R): This allows complete separation of oxygenated and deoxygenated blood.
A. Both A and R are true, but R is not the correct explanation.
B. Both A and R are true, and R is the correct explanation.
C. A is true, but R is false.
D. A is false, but R is true.

Correct Answer: Option C


Explanation:
Amphibians have two atria and one ventricle; mixing of blood occurs because of the single ventricle. Complete separation is achieved only in four-chambered hearts. So A true, R false.

This question belongs to: Science Biology
Question #3
In biotechnology, the 'PCR' (Polymerase Chain Reaction) technique requires a thermostable DNA polymerase. The most commonly used enzyme for this is:
A. Reverse transcriptase
B. DNA polymerase I
C. Taq polymerase
D. T7 polymerase

Correct Answer: Option C


Explanation:
PCR involves repeated cycles of high-temperature denaturation (around 94°C) to separate the DNA strands. Normal DNA polymerases would be destroyed at these temperatures. Therefore, a thermostable DNA polymerase is required. Taq polymerase, isolated from the thermophilic bacterium Thermus aquaticus found in hot springs, is the most commonly used enzyme because it can withstand the high denaturation temperatures without losing its activity, eliminating the need to add fresh enzyme after each cycle.

This question belongs to: Science Biology