Page 19 - Biology - XII

Q15. Which alternate enzyme can be used to break plant cells?
(a) Cellulase (b) Lysozyme (c) Chitinase (d) None of these

Q16. The isolated DNA strands are
(a) fi brous, whitish, and clear jelly like (b) granular, yellow, and hard
(c) Fibrous, yellowish, and aqueous (d) granular

Q17. During the process of isolation of DNA after centrifugation DNA will be present in
(a) base of the solution (b) middle of the solution
(c) on top-supernatant liquid (d) absent

Q18. For isolation of DNA the speed of centrifugation should be
(a) 8000 rpm for about 10 min (b) 8000 rpm for about 5 min
(c) 1000 rpm for about 10 min (d) 1000 rpm for about 5 min

Q19. DNA is soluble in
(a) water (b) organic solvent (c) alcohol (d) ether

Answer key
1. (b), 2. (d), 3. (c), 4. (d), 5. (b), 6. (a), 7. (d), 8. (a), 9. (d), 10. (d), 11. (a), 12. (c), 13. (c), 14. (a),

15. (d), 16. (a), 17. (a), 18. (d), 19. (a)

Assertion-Reason Type Questions

These consist of two statements—Assertion (A) and Reason (R). Answer these questions by selecting
the appropriate option given below:
a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true, but R is not the correct explanation of A.

c. A is true, but R is false.
d. A is false, but R is true.
1. Assertion (A) : The double-stranded DNA is denatured by subjecting it to high temperature of
94°C for 15 seconds.

Reason (R) : One of the separated strands of the DNA is destroyed during denaturation and
the other act as a template.
2. Assertion (A) : Genetic engineering can overcome the drawbacks of traditional hybridisation.
Reason (R) : Genetic engineering can create desired DNA sequences to meet specifi c
requirements.
Answer key

1. (c), 2. (a)

18