Case study- Replication-A scientist is replicating human DNA in a test tube ..

QUESTION OF THE DAY

A scientist is replicating human DNA in a test tube and has added intact DNA, the replisome complex, and the four deoxyribonucleoside triphosphates.

DNAr  Replication

 

Figure- DNA Replication

To the surprise of the scientist, there was no DNA synthesized, as determined by the incorporation of radio-labeled precursors into acid-precipitable material. The scientist’s failure to synthesize DNA is most likely due to a lack of which of the following in his reaction mixture?

A. Reverse transcriptase

B. Ribonucleoside triphosphates

C. Templates

D. Dideoxynucleoside triphosphates

E. Sigma factor

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2 Responses

  1. Seema says:

    B. Ribonucleoside triphosphates. DNA synthesis requires the synthesis of primers upon which deoxyribonucleotides will be added. The primers are composed of ribonucleotides (DNA primer is a DNA dependent RNA polymerase) and the scientist forgot to add NTPs to the reaction mixture ( deoxyribonucleotides are not recognized by DNA primase and cannot be used to synthesize a primer). Reverse transcriptase is not required for DNA synthesis from DNA template (as here). Sigma factor is the factor required for bacterial RNA synthesis, not for eukaryotic DNA synthesis.

  2. D, I think you would need some sort of energy to replicate.

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