NEET Biology 2 — Questions and Answers
Question 1: Which enzyme is responsible for unwinding the DNA double helix during replication?
- DNA polymerase
- Helicase (Correct answer)
- Ligase
- Primase
Correct answer: Helicase
Helicase breaks hydrogen bonds between base pairs to unwind the double helix at the replication fork.
Question 2: The process by which plants lose water through aerial parts other than stomata is called:
- Transpiration
- Guttation
- Cuticular transpiration (Correct answer)
- Lenticular transpiration
Correct answer: Cuticular transpiration
Cuticular transpiration is water loss through the cuticle of leaves, accounting for about 5–10% of total transpiration.
Question 3: Which of the following correctly describes the lac operon in the presence of lactose and absence of glucose?
- Repressor binds operator; operon OFF
- CAP-cAMP activates; operon ON (Correct answer)
- Repressor binds operator; operon ON
- CAP-cAMP represses; operon OFF
Correct answer: CAP-cAMP activates; operon ON
Low glucose raises cAMP, allowing CAP-cAMP to bind and activate transcription; lactose removes the repressor, so the operon is fully ON.
Question 4: Biotic potential refers to:
- Maximum population size in an environment
- Intrinsic rate of natural increase under ideal conditions (Correct answer)
- Carrying capacity of a habitat
- Resistance of a population to disease
Correct answer: Intrinsic rate of natural increase under ideal conditions
Biotic potential (r) is the maximum reproductive rate of a population under ideal, unlimited environmental conditions.
Question 5: In which phase of meiosis does crossing over occur?
- Zygotene of Prophase I
- Pachytene of Prophase I (Correct answer)
- Diplotene of Prophase I
- Metaphase I
Correct answer: Pachytene of Prophase I
Crossing over (chiasmata formation) occurs during pachytene of Prophase I when homologous chromosomes are fully synapsed.
Question 6: Which blood group is considered the universal recipient?
- A
- B
- O
- AB (Correct answer)
Correct answer: AB
AB blood group individuals have no anti-A or anti-B antibodies, so they can receive blood from any ABO group.
Question 7: The primary photosynthetic pigment in higher plants that directly participates in the light reaction is:
- Carotenoids
- Chlorophyll b
- Chlorophyll a (Correct answer)
- Xanthophylls
Correct answer: Chlorophyll a
Chlorophyll a is the primary reaction center pigment that directly converts light energy to chemical energy in photosystems.
NEET Biology 2
Which enzyme is responsible for unwinding the DNA double helix during replication?