DNA encodes instructions for protein synthesis. Some of the first steps in the p
ID: 168196 • Letter: D
Question
DNA encodes instructions for protein synthesis. Some of the first steps in the process are the unwinding of the DNA double helix by the enzyme RNA polymerase and the transcription of a stretch of DNA into messenger RNA (mRNA); mRNA in turn serves as a template for protein syn- thesis. Transcription is not instantaneous: RNA polymerase processes about 40 base pairs per sec- ond (40 bp/s) at room temperature. However, only about 1.5% of the nucleotide sequences in hu- man DNA is actually transcribed into mRNA. Show the calculation of the number of hours required for the transcription of 1.5% of the nucleotide sequences of a 250 Mbp DNA molecule.
Explanation / Answer
Ans. Given,
Total bp sequence of DNA = 250 Mbp = 250 x 106 bp
Number of bp being transcribed = 1.5 % of (250 x 106 bp)
= 3.75 x 106 bp
Time taken for transcription= Total number of base pairs / Transcription rate
= (3.75 x 106 bp) / ( 40 bp/ s)
= 9.375 x 104 s
= [(9.375 x 104 s)/ 3600 ] hr ; [1 hr = 3600s]
= 26.04 hr
Thus, time taken for transcription = 26 hrs
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