Question

The following DNA coding sequence is at the beginning of a coding region of the wildtype MCB gene

(wildtype allele) DNA   5’ C A T G A A A T G G* G A G C C T G A A G G A 3’

(mutant allele) DNA     5’ C A T G A A A T G A* G A G C C T G A A G G A 3’

There has been a base change mutation at the position marked with an asterisk that changes the G to an A in the mutant allele.

1. ) How will this mutation influence transcription of the MCB gene?

2. ) How will this mutation influence translation?

3.) What type of mutation is this (silent, missense, nonsense, frameshift.)

Answer 1

The given sequence of the wild type coding strand of the DNA:

5’ C A T G A A A T G G G A G C C T G A A G G A 3’

So, the template strand DNA : 3' GTA CTT TAC CCT CGG ACT TCC T 5'

The sequence of mRNA will be: 5' CAU GAA AUG GGA GCC UGA AGG A 3'

Amino acid sequence: HIS GLU MET GLY ALA STOP

The given sequence od the mutant allele coding strand DNA is:

5' C A T G A A A T G A* G A G C C T G A A G G A 3'

The template strand DNA: 3' GTA CTT TAC TCT CGG ACT TCC T 5'

the sequence of the mRNA will be: 5' CAU GAA AUG AGA GCC UGA AGG A 3'

The amino acid sequence will be:  HIS GLU MET ARG ALA STOP

1) During transcription, mRNA is formed using template DNA as the template. Here, the mRNA formed due to the mutant allele has a different base as compared to wild type mRNA.

Wild type mRNA = 5' CAU GAA AUG GGA GCC UGA AGG A 3'

mutant type mRNA = 5' CAU GAA AUG AGA GCC UGA AGG A 3'

The G is replaced by A in mutant type.

2) The translation is the process in which the polypeptide chain is formed using mRNA as a template.

wild type protein sequence: HIS GLU MET GLY ALA STOP

mutant type protein sequence:   HIS GLU MET ARG ALA STOP

Here, GLY is replaced by MET due to the mutation.

3) Here one amino acid is changed, this type of mutation is known as a missense mutation.

Please hit on the like button if you are satisfied with the answer. Give comments for further clarification/assistance. Thanks! Have a good day.