14.06 1. Excision repair is considered to be a nonspecific repair pathway becaus

Question

14.06

1.  

Excision repair is considered to be a nonspecific repair pathway because:

A. undamaged bases on the complementary strand of DNA are removed.

B. the bases on the complementary strand are used for resynthesis.

C. it can be carried out by replicative polymerases alone.

D. DNA replication itself activates this pathway.

E bases surrounding the damaged base are also removed from the DNA.

2.  

A thymine dimer is the covalent linkage between two adjacent thymine bases in the DNA caused by UV radiation.

True

False

3.  

Endocision repair is a nonspecific form of repair in which a damaged region in the DNA is removed and replaced by DNA synthesis.

True

False

4.  

Errors from replication, which seldom occur, and damage induced by chemical agents or UV light, do not lead to mutations.

True

False

5.  

Without repair mechanisms, cells would accumulate mutations until inviability occurred.

True

False

6.  

Some repair systems are nonspecific, such as excision repair that removes and replaces damaged regions.

True

False

7.  

The enzyme photolyase uses energy from ATP to cleave thymine dimers caused by UV light.

True

False

8.  

The enzyme photolyase uses energy from ATP to cleave thymine dimers caused by UV light.

True

False

14.2

9.  

The free hydroxyl group is attached to what carbon of the sugar in nucleic acids?

A. 5

B. 4

C. 3

D. 2

E. 1

10.  

According to Chargaff's rules, if the DNA of a species contains 20% thymine, what percent of guanine will it contain?

A. 80%

B. 30%

C. 60%

D. 20%

E. 40%

Explanation / Answer

1. C

2. True

3. True

4. False

5. True

6. True

7. True

8. True

9. A

10. B                  

According to Chargaff’s rule, [A]+[G]=[C]+[T]

[A]+[G]+[C]+[T]=100%

Adenine (A) is paired to Thymine (T), A=T

Cytosine (C ) is paired to Guanine (G), G=C

Here [A]=20% therefore % of [T] is also 20%.

therefore [G]+[C]=100 - 40 = 60 %.

[G]=30% and [C]=30%

Ans. is [A]=20%, [T]=20%,[G]=30%, [C]=30%

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