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Types of Mutations: Substitution, Insertions, Deletion and Frameshifts
#9
OK, I am confused! Are insertions and deletions considered point mutations or frameshift mutations? Different sources are labeling them as different things. I actually have a textbook that says they are both point AND frameshift! They cannot be both, can they? I would assume they would be frameshift mutations since they are affecting more than one "point" in the gene. Could anyone help me clear this up and put the issue to rest? Thanks!
#10
(03-29-2017, 10:14 AM)forester7 Wrote: OK, I am confused! Are insertions and deletions considered point mutations or frameshift mutations? Different sources are labeling them as different things. I actually have a textbook that says they are both point AND frameshift! They cannot be both, can they? I would assume they would be frameshift mutations since they are affecting more than one "point" in the gene. Could anyone help me clear this up and put the issue to rest? Thanks!

Hello forester7,

Frameshift is a consequence and Insertions/ Deletions are the causes.

Let's say I have this reading frame:

AAC-ATC-CAG-CCA-TTC.....

And now, an insertion of 1 base takes place at the third spot:
AAA-CAT-CCA-GCC-ATT-C.... (this single base insertion is a 'Point Mutation' in this case as it involved/ affected only 1 nucleotide [mutations affecting/ involving only 1-2 nucleotides are termed point]. But this point insertion led to the change of entire reading frame! Hence the consequence of this Insertion type point mutation is 'Frameshift mutation'].


If there was an insertion of 3 bases, then reading frame won't have changed. So it would have been an Insertion type mutation only.

Same goes for deletion process.

Lesson to be taken is:

It is not obligatory that 'One event leads to One Mutation only'. A single event can have numerous consequences. Single or double point mutations are most dangerous ones as they lead to frameshifts (a consequence). 


Hope it clears your doubt to some extent..
Sunil Nagpal
MS(Research) Scholar, IIT Delhi (Alumnus)
Advisor for the Biotech Students portal (BiotechStudents.com)
Computational Researcher in BioSciences at a leading MNC


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#11
(03-29-2017, 01:18 PM)SunilNagpal Wrote:
(03-29-2017, 10:14 AM)forester7 Wrote: OK, I am confused! Are insertions and deletions considered point mutations or frameshift mutations? Different sources are labeling them as different things. I actually have a textbook that says they are both point AND frameshift! They cannot be both, can they? I would assume they would be frameshift mutations since they are affecting more than one "point" in the gene. Could anyone help me clear this up and put the issue to rest? Thanks!

Hello forester7,

Frameshift is a consequence and Insertions/ Deletions are the causes.

Let's say I have this reading frame:

AAC-ATC-CAG-CCA-TTC.....

And now, an insertion of 1 base takes place at the third spot:
AAA-CAT-CCA-GCC-ATT-C.... (this single base insertion is a 'Point Mutation' in this case as it involved/ affected only 1 nucleotide [mutations affecting/ involving only 1-2 nucleotides are termed point]. But this point insertion led to the change of entire reading frame! Hence the consequence of this Insertion type point mutation is 'Frameshift mutation'].


If there was an insertion of 3 bases, then reading frame won't have changed. So it would have been an Insertion type mutation only.

Same goes for deletion process.

Lesson to be taken is:

It is not obligatory that 'One event leads to One Mutation only'. A single event can have numerous consequences. Single or double point mutations are most dangerous ones as they lead to frameshifts (a consequence). 


Hope it clears your doubt to some extent..

That definitely helps! Thanks!
  




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