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  #1  
Old 02-20-2011
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DNA How do we calculate this gene mRNA bases question

Question:

A gene encodes a protein with 150 amino acids. There is one intron of 1,000 bps , a region of 5' UTR of 100 bp, and a 3' UTR of 200 bp. In the final processed mRNA, how many bases lie between the start AUG codon and the final termination codon ?

A) 1,750
B) 750
C) 650
D) 450
E) 150

Answer: ? (Please provide an explanation for how you reached your answer)
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  #2  
Old 02-20-2011
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Answer is D.

A single amino acid is coded by three base pairs. A protein with 150 amino acids must have 150 * 3 = 450 base pairs.

In the final processed mRNA, introns are spliced out ( removed ); we have only exons.
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Old 02-20-2011
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D. Because each amino acid is encoded by 3 bases. so 150x3=450. You do not include UTR and introns ecause they are not translated.
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Default D

Yes D is the correct answer!
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Old 02-21-2011
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but total bases In the final processed mRNA it will be 5UTR + 3UTR + 3x150

= 750 (plus poly A tail ,not given here)

How do we calculate this gene mRNA bases question-dsc00453.jpg
click image to enlarge
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Old 02-21-2011
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Quote:
Originally Posted by rsin21 View Post
but total bases In the final processed mRNA it will be 5UTR + 3UTR + 3x150

= 750 (plus poly A tail ,not given here)
The Q is asking about base pairs between stop and start codons. That doesn't include 5'UTR, 3'UTR, or poly A tail. Count between AUG (start codon) and UAG (stop codon).
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Old 02-21-2011
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Quote:
Originally Posted by drahmednawaz View Post
The Q is asking about base pairs between stop and start codons. That doesn't include 5'UTR, 3'UTR, or poly A tail. Count between AUG (start codon) and UAG (stop codon).
I know that....just making it clear if the question asked just for final mRNA

thanks nyways
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Old 02-22-2011
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i believe it's ( d )
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