QUESTION 1 Which enzyme is responsible for the unwinding of DNA double strands t

Question

QUESTION 1 Which enzyme is responsible for the unwinding of DNA double strands to initiate DNA replication? OA Topoisomerase OB. DNA polymerase l OG. DNA polymerase Helicase QUESTION 2 Without the topoisomerase, what will happen to DNA replication? OA DNA strands will not be able to unwind. OB. There will not be any primers synthesized. OC.The replication fork will not be able to proceed. OD. DNA strands will be degraded. QUESTION 3 Who is responsible for synthesizing primers for DNA replication? What kind of primers are they? OA DNA primase..ANA primers OB DNA primase...DNA primers DNA polymerase l RNA primers OD. DNA polymerase L..DNA primers QUESTION 4 Suppose that an E.colstrain has a deletion mutation in the gene that encodes for the DNA ligase, what will happen to this Ecoli strain? AThe strain will die. OB.The strain will grow slowy OC. The strain will grow nomally OD. The strain vwill grow faster.

Explanation / Answer

1) The correct option is D. Helicase.

DNA helicase is an enzyme, which unwinds the DNA double helix by breaking the hydrogen bonds down the center of the strand. It initiates at a site, known as origin of replication and forms a replication fork by the separation of the two sides of the parental DNA.

2) The correct option is A. DNA strands will not be able to unwind.

Topoisomerases are enzymes, which take part in the overwinding and underwinding of DNA. The winding problem of DNA arises due to the intertwined character of its double-helical structure. During the process of DNA replication and transcription, DNA becomes overwound ahead of a replication fork.

3) The correct option is C. DNA polymerase I - RNA primers.

DNA polymerases enzymes carry all forms of DNA replication. DNA polymerases cannot initiate the synthesis of new strands, but can only extend an existing DNA or RNA strand paired with a template strand. To initiate the synthesis, a short fragment of RNA known as primer, must be created and paired with the template DNA strand. A DNA polymerase extends the primed segments and forms Okazaki fragments. The RNA primers are then removed and replaced with DNA and the fragments of DNA are connected together by DNA ligase.

4) The correct option is B. The strain will grow slowly.

Suppose that an E.coli. strain has a deletion mutation in the gene that encodes for the DNA ligase, this E.coli. strain will grow slowly.

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