Question

There is a mutation in a codon-sequencing triplet of DNA. The sequence of 3' ATG 5' was mutated so that now it reads 3' ATC 5. What kind of mutation is this? SECOND POSITION с A U phenyl- slanine tyrosine cysteine U U с А serine leucine stop stop stop tryptophan G histidine U С A с leucine proline arginine FIRST POSITION glutamine THIRD POSITION isoleucine asparagine G U с А G serine А threonine methionine lysine arginine valine aspartic acid glutamic U с А alanine G glycine acid G and start Frameshift Nonsense Missense Silent

Answer 1

Answer Option 2 .Nonsense mutation.

Nonsense mutation is a genetic mutation in a DNA sequence .It is due to the substitution of a single base pair results in the appearance of a stop codon.Here the sequence 3’ATG5’ was mutated to 3’ATC5’.The codon UAC codes for tyrosine changed to UAG which is the stop codon.

Option 1 is wrong .Frame shift mutation is caused by a deletion or insertion in a DNA sequence that results in disruption of reading frame .This will affect the sequence of amino acids.

Option 3 is incorrect.In missense mutation single nucleotide change results in a wrong codon so that wrong amino acid is incorporated into a protein. Example Sickle cell disease due to occurrence of amino acid valine instead of glutamic acid.

Option 4 is also wrong.Silent mutations are base substitutions which do not affect the sequence of amino acids.For example if codon AAA is changed to AAG the same amino acid lysine will be incorporated into the peptide chain.