Question

2. After each sentence below, note whether the sentence is true or false. If false, cross out one incorrect word in the sentence and write the correct one above it. a. DNA polymerase requires a short primer made of DNA with a 3' OH group to begin chromosome replication. b. Semi-conservative DNA replication means that a newly synthesized daughter chromosome will be fully- methylated c. The lagging strand of newly synthesized DNA will have many more primers compared to the leading strand. d. The bacterial SOS response is activated in the presence of excessive ssRNA that accumulates in the presence of high levels of mutation. 3. Give three separate reason for why the process of DNA replication of bacterial chromosomes absolutely requires lagging strand synthesis.

Answer 1

A. False

The primer formed during the process of DNA replication is not made up of DNA. It is made up of RNA and is synthesized by enzyme Primase. Primer provides free 3 Prime hydroxyl group for the synthesis of DNA.

B. False

Semi conservative model of DNA replication means that the daughter DNA molecule which is newly formed contain one parental strand and one newly synthesized strand. Because one of the parental strand is retained in the daughter DNA molecule, it is called as semi conservative model of DNA replication.

C. True

Lagging strand is synthesized in a discontinuous manner. Multiple RNA primer are formed on this strand and to each primer, One Short molecule of DNA is synthesized. This molecule is called as okazaki fragment. When the replication is completed all the okazaki fragments are joined together by DNA ligase enzyme. The Primers are removed with the help of DNA polymerase 1.

4. False

Bacterial SOS response is a mismatch repair system which stimulates in the presence of single stranded DNA and not RNA.

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