17. Which of the following is the correct base pairing of DNA and RNA nucleotide

Question

17. Which of the following is the correct base pairing of DNA and RNA nucleotides?

DNA: ATTACGTCC

a. RNA UAAUGCUGG

b. RNA UAATGCAGG

c. RNA UAAUGCAGG

d. RNA TAATGCAGG

18. T or F. DNA replication takes place during the S phase of the cell cycle.

True

False

19. T or F. Semiconservative replication results in 1 template double helix and 1 newly synthesized "daughter" double helix.

True

False

20. T or F. Exposure to ultraviolet light, X-rays, and other agents (OH radical, H2O2) damages DNA. UV radiation is a major risk factor for skin cancer and malignant melanoma. One of the most frequent alterations caused by UV exposure is the formation of Thymine dimers (T‹ ›T) base pairing. These lesions, if not repaired, can result in skin cancers. Sunscreens to prevent UV induced skin cancers are recommended.

True

False

21. Two mechanisms that repair damaged DNA are __________________ and _____________________.

a. night repair

b. excision repair

c. photo repair

d. answers b and c are correct.

22. The location where the DNA molecule becomes unzipped into two single strands is called a __________________________________.

a.replication spoon

b. replication fork

c. replication knife

d. replication road

Explanation / Answer

17. Ans- c. RNA UAAUGCAGG

      DNA: ATTACGTCC

    RNA: UAAUGCAGG

RNA contains four nitrogenous bases such as adenine, guanine, cytosine and uracil.

18. Ans- True

           DNA replication takes place in S (synthesis) phase.

19. Ans- True

            Semi conservative replication is the process in which double helix DNA is formed that contains one parental strand and one newly synthesized strand.

20.Ans-True

              DNA is damaged by ultraviolet light, ionizing radiation, and certain chemical agents.Melanomas and skin cancer are mainly caused by exposure to ultraviolet (UV) rays. After absorbing UV light, thymine becomes reactive with an adjacent thymine molecule and form cyclobutane dimer. As a result, RNA polymerase unable to make an accurate mRNA and to form incorrect protein. If these lesions are not repaired then the skin cells become cancerous. Sunscreens help prevent the ultraviolet (UV) radiation to reach the skin.

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