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Direct Repair

View the animation below, then complete the quiz to test your knowledge of the concept.

1UV light and other ionizing radiations damage DNA molecules by...
A)creating guanine dimmers between adjacent guanines in the DNA chain.
B)creating adenine dimmers between adjacent adenines in the DNA chain.
C)creating thymine dimmers between adjacent thymines in the DNA chain.
D)creating uracil dimmers between adjacent uracils in the DNA chain.
E)creating cytosine dimmers between adjacent cytosines in the DNA chain.

2These dimmers weaken...
A)hydrogen bonds.
B)sulfide bonds.
C)covalent bonds.
D)ionic bonds.
E)all of these.

3These dimmers are repaired by...
A)the enzyme DNA photolyase.
B)exposure to light.
C)transfer of an electron to the dimer.
D)A and B.
E)A, B and C.

4Chemical agents can cause mutations by inducing ethylation of guanine residues in DNA.

5The enzyme ethylguanine-DNA ethyltransferase prevents DNA mutations from occurring.

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