NEET Biology 5 — Questions and Answers
Question 1: Which part of the brain is primarily responsible for regulating body temperature, hunger, and thirst?
- Cerebellum
- Medulla oblongata
- Hypothalamus (Correct answer)
- Thalamus
Correct answer: Hypothalamus
The hypothalamus acts as the master regulator of homeostasis, controlling temperature, hunger, thirst, and circadian rhythms.
Question 2: In which type of RNA secondary structure do complementary base sequences within the same strand pair to form a stem-loop?
- Ribosome
- Anticodon loop of tRNA
- Hairpin loop (Correct answer)
- Poly-A tail
Correct answer: Hairpin loop
A hairpin loop (stem-loop) forms when complementary sequences within a single RNA strand fold back and base-pair with each other.
Question 3: Which of the following conditions is caused by trisomy of chromosome 21?
- Klinefelter syndrome
- Turner syndrome
- Down syndrome (Correct answer)
- Patau syndrome
Correct answer: Down syndrome
Down syndrome (trisomy 21) results from three copies of chromosome 21 and is the most common autosomal trisomy.
Question 4: The enzyme telomerase adds telomeric sequences using which mechanism?
- Uses a DNA template from the chromosome
- Uses its own RNA component as template (Correct answer)
- Uses a protein template
- Uses an external RNA primer
Correct answer: Uses its own RNA component as template
Telomerase is a reverse transcriptase that uses its internal RNA subunit as a template to extend telomeric DNA repeats.
Question 5: Which of the following best describes the role of auxin in phototropism?
- Auxin is destroyed on the light side, reducing growth
- Auxin migrates to the shaded side, promoting cell elongation (Correct answer)
- Auxin promotes equal growth on both sides
- Auxin inhibits growth on both sides equally
Correct answer: Auxin migrates to the shaded side, promoting cell elongation
In phototropism, auxin moves laterally to the shaded side of the shoot tip, causing greater elongation and bending toward light.
Question 6: The conversion of fibrinogen to fibrin during blood clotting is catalyzed by:
- Prothrombin
- Thrombin (Correct answer)
- Factor X
- Vitamin K
Correct answer: Thrombin
Thrombin (activated from prothrombin) proteolytically cleaves fibrinogen to produce fibrin monomers that polymerize into clots.
Question 7: Which of the following is the correct sequence of events in the cardiac cycle?
- Atrial systole → ventricular systole → joint diastole (Correct answer)
- Ventricular systole → atrial systole → joint diastole
- Joint diastole → ventricular systole → atrial systole
- Atrial systole → joint diastole → ventricular systole
Correct answer: Atrial systole → ventricular systole → joint diastole
The cardiac cycle proceeds: atrial systole (0.1s) → ventricular systole (0.3s) → joint diastole (0.4s), completing in ~0.8 seconds.
NEET Biology 5
Which part of the brain is primarily responsible for regulating body temperature, hunger, and thirst?