Stop codon

Question text:

The following DNA sequence occurs near the middle of the coding region of a gene.
 DNA   5'  A A T G A A T G G* G A G C C T G A A G G A  3'   

 

There is a G to A base change at the position marked with an asterisk. Consequently, a codon normally encoding an amino acid becomes a stop codon. 
1.  How will this alteration influence DNA replication?
2.  How will this alteration influence transcription?
3.  How will this alteration influence translation?

Background information:

This question was previously referred to as "Central Dogma".

These set of items have been converted from the Genetics Concept Assessment by Smith et al.

For the constructed respons version, students are given one set-up paragraph, then given three separate question prompts (one prompt about each central dogma process) and separate text boxes to input their response.

Original items:

#11:  The following DNA sequence (coding strand) occurs near the middle of the coding region of a gene.

DNA

    50
5'-A A T G A A T G G G A G C C T G A A G G A G -3'

The corresponding mRNA sequence is shown below. Note that the coding strand of DNA has the same sequence as the mRNA, except that there are U's in the mRNA where there are T's in the DNA. The first triplet of nucleotides AAU (underlined) is in frame for coding, and encodes Asparagine as the codon table indicates.

mRNA

   50
5'-A A U G A A U G G G A G C C U G A A G G A G -3'

Which of the following DNA mutations is almost certain to result in a shorter than normal mRNA?

a) A¨G at position 50
b) G¨A at position 53
c) C¨A at position 58
d) None of the above

#12  For the same DNA sequence, which of the following DNA mutations is almost certain to result in a shorter than normal protein?

a) T¨C at position 59
b) A¨G at position 61
c) Insertion of a G after the G at position 54
d) None of the above

 

 

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This material is based upon work supported by the National Science Foundation (DUE grants: 1438739, 1323162, 1347740, 0736952 and 1022653). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.