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Question: In a DNA, the sequence of triplet base is- ACG AGG ACU GCA UAC CA - which of the below series shows frameshift mutation?

  • A

    A CGA GGA CUG CAU ACC A-

  • B

    ACG GGA ACU GCA UAC CA-

  • C

    ACG GGA ACT GCA TAC CA-

  • D

    ACG UAA ACU GCA UAC CA-

Posted by: Simi Sharma on: 13 Mar, 2020
Answer

Hello Shabnam,

 

The answer is obviously   A.

This is because  the Frame has shifted from the original CODON which was ACG  and has shifted to the Right leaving  A by itself, the new CODON formed by the Shift is CGA.

 

Frame shifts happen due to whaat are called INDELS (Insertions and Deletions)

 

A brief explanation is as follows:

step by step

 

1.A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read.

2.A DNA sequence is a chain of many smaller molecules called nucleotides.

3. DNA (or RNA) nucleotide sequences are read three nucleotides at a time in units called codons, and each codon corresponds to a specific amino acid or stop signal. 

4.During translation, the sequence of codons is read in order from the nucleotide sequence to synthesize a chain of amino acids and form a protein.

5. Frameshift mutations arise when the normal sequence of codons is disrupted by the insertion or deletion of one or more nucleotides, provided that the number of nucleotides added or removed is not a multiple of three

 

Hope this explanation has helped.

 

Thanks & regards,

 

Dr Shyam Suryarao

Answer

Answer to the above question is 'A' option, as in Frameshift muatation the reading frame of triplet codons changes. It means the triplet codons on mRNA will not code for same amino acid as it would prior to mutation. In restof the 3 options individual nucleotide may have chaged but they have same reading frame as in the question.

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