Question

1)Repairing damaged DNA is essential to maintaining the integrity of the genome. One type of repair is known as nucleotide excision repair. In this system, which order do the necessary enzymes act? A) exonuclease, DNA polymerase III, RNA primase B) helicase, DNA polymerase I, DNA ligase C) DNA ligase, nuclease, helicase D) DNA polymerase I, DNA polymerase III, DNA ligase E) endonuclease, DNA polymerase II, DNA ligase

2) What might be the result if all cells had functioning telomerase? A) cells would be able to divide indefinitely B) DNA replication would be hindered C) there would be no effect D) defects in DNA replication E) chromosome length in gametes would increase with every generation

3) DNA polymerase requires an existing nucleotide to begin new synthesis of a DNA strand. What would be the primer for the following DNA template sequence: Include 3' and 5'. 3' ATTGCATG 5'

4) Nucleases are enzymes that break phosphodiester bonds between nucleotides in a nucleic acid. Which of the following statements concerning these enzymes is incorrect? A) Endonucleases break bonds within the DNA strand. B) Exonucleases break the bond of the terminal nucleotide of a DNA strand. C) Endonucleases are involved in telomere extension. D) Nucleases are involved in excision repair of DNA.

5) Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder in which the affected individual cannot tolerate exposure to UV light. These individuals have a high incidence of skin cancer, often before the age of 10. The absorption of UV light is known to occasionally cause the formation of thymine dimers which can lead to skin cancer. Based on these clinical characteristics, what is a likely cause for this disorder? A) defects in DNA replication B) a mutation in DNA ligase C) shortened telomeres D) defects in nucleotide excision repair E) a mutation of DNA polymerase III

Answer 1

QUESTION-1

ANSWER

Repairing damaged DNA is essential to maintaining the integrity of the genome. One type of repair is known as nucleotide excision repair. In this system, the order necessary enzymes act

B) helicase, DNA polymerase I, DNA ligase

EXPLANATION

Nucleotide excision repair removes a bulky pack of DNA.

It removes the damaged DNA and replaces them.

Helicase enzyme opens the DNA strands and creates a bubble.

Another excision enzyme removes the damaged part.

Polymerase enzyme replaces the missing parts.

In the end DNA ligase joins them by sealing the gap.

QUESTION-2

ANSWER

The result if all cells had functioning telomerase, would be

A) cells would be able to divide indefinitely

EXPLANATION

Telomerase is the enzyme that maintains the end of the DNA.

Inactivation of telomerase leads to the senescence of the cell.

Telomerase prevents loosing of nucleotide bases from chromosome ends.

If the cells had a functioning telomerase ten then would proliferate indefinitely.

QUESTION-3

ANSWER

The primer for the sequence 3' ATTGCATG 5' is

5' UAACGUAC 3'

• Primer is required to initiate the DNA replication.
• It is made up of a short stretch of the nucleotide sequence.

GOOD LUCK.