Mutation Vs polymorphism - Mutation Vs polymorphism (Apr/05/2006 )

hi there all...

Its an old question but one that doesnt seem to find a consensus in terms of an answer...i would like to hear what the true definition of mutation Vs polymorphism is.

I need verfication on MY understanding...and if im wrong could i be corrected.Thankyou.

Yes both are changes but is more truthful to explain it as
a mutation: is induced from outside the cell: by an exogenous factor, is inheritable and
does not necessarily harmful to the host. Therefore a mutation is individualised and
will therefore occur in less than 1% of the population.


A polymorphism: is induced from within the cell( i.e. through evolution the cell changes to conform
to the changing environment to survive...(after all the basic function of a cell is to
use all its various pathways and mechanism to surivive and thereby maintaining
its function within the host.)), is heritable but is not necessarily harmful to the
host. This heritable change will occur in at least 1% of the population.

If examples had to be given , which examples will be classified under mutations and which under polymorphism.??

Thankyou for your help

143

The explanation I've been given is that a mutation causes disease whereas a polymorphism does not.

I don't fully agree with you on this one Helena. Maybe it depends on the species you're working on, but I'm working on an RNA virus with a reverse transcription step in its lifecycle. RT has no proofreading activity so there's a lot of random "mutations" in there.

The thing is that due to the large variety in its genome, there's been made up a classification into subtypes (it's HIV-1 group M we're talking about). As you know, there are some antiretroviral compounds used for treatment of HIV-infected people. Without going into detail, these virus in these individuals will get mutations that will cause the virus to be less susceptible to certain drugs (the cause for therapy failure). Now, for certain mutations it is known that they only are "induced" due to therapy in certain subtypes but are omnipresent in other subtypes (and are therefor within this subtype calles "polymorphisms").

A mutation is more like an event. It's something that happens and changes a genome, usually they go unnoticed, sometimes they cause a disease and very rarely they might give a selective advantage and alter evolution.

A polymorphism refers to a variation in genomes in one species. I think its indeed at least 1 % such a variation must occur within a population. As with mutations they might go unnoticed, but they usually have small effects on phenotypes: not as much as mutations. Eg, hair color, enzyme effectiveness, HLA receptors, all kinds of stuff. They might predispose for diseases, eg the APOE (?) and alzheimer.

I don't think the source of the genomic change (so exogenous or endogenous) has something to do with it.

Hope it helps

David

A polymorphism is a mutation that has been proven to have a prevelance above a certain % in a given population

A mutation is a change from the norm/reference, a polymorphism is an excepted norm.
Polymorphisms are genetically past on -spread through the germline by selection or genetic drift- while mutations do not have to.

Hi 143,

Good question.

Dictionaries are not clear on this point. Some specifically define a mutation as a heritable genetic change that is caused by a mutagen, that is, some external agent such as radiation or chemicals. Others are more general and define it only as a heritable genetic change caused by external agents (mutagens) or internal events such as replication errors, unequal crossing-over, gene conversion, etc. Polymorphism seems to me to be a more general term simply meaning "many forms", as the name implies " poly-morphs". My personal internal dictionary identifies mutation as an event, whether it is a point mutation, deletion, insertion, inversion, duplication, whatever, that happens once in an individual and then either disappears if that individual does not breed, or increases in frequency in a population through selection or neutral genetic drift. A polymorphism is simply the state of multiple forms. So, mutations are events that generate polymorphisms.

But can recombination, which can generate new alleles of a gene and therefore polymorphism of that gene, be considered as a mutational event? I think not. So perhaps mutation is only one source of polymorphism.

As I said, good question.