Mutation

[shabnam]

What happens when point mutation occurs in the somatic cell of a person?Of course the mutation can't be transferred,but does it spread to other cells?and does it manifest itself in the affected individual? I'm sorry if this is a stupid question but I've asked two of my teachers and they don't seem to get my question.

[Dak]

somatic cells are 'out of the germline', so they won't be passed on to any offspring (as in childeren), but they will be passed on to any offspring-cells.

 

eg, haematopoietic stem-cells (marrow-bown cells from whence blood-cells are made) are somatic, so if i have a mutation in one of them it will not be passed on to my childeren; however, any other haematopoietic stem-cells, or any red/white-blood-cells that are produced from that mutant haematopoetic cell will inherit the mutation.

 

the mutation won't 'spread' as such, inasmuch as other, non-mutant cells won't somehow aquire the mutation unless they are actually decended from the mutant cell, and as for manifesting -- if the point mutation actually has an effect (eg, knocks out a gene), then all the blood-cells that are desended from the haem-stem-cell will express the mutation; in this case, i'd have a handfull of blood-cells that didn't make a certain protien, for example.

 

the reason germ-cell mutations can be inherited is that one of the daughter cells that inherits the mutation could be a sperm/ova, in which case the zygote/foetus would posess the mutation.

 

hope that's clear? (and it's not a stupid question btw)

[lucaspa]

What happens when point mutation occurs in the somatic cell of a person?Of course the mutation can't be transferred,but does it spread to other cells?and does it manifest itself in the affected individual? I'm sorry if this is a stupid question but I've asked two of my teachers and they don't seem to get my question.

 

Just to add to Dak's excellent reply, the mutation is inherited by any daughter cells (progeny) of the mutated cells. And yes, the mutation can manifest itself in the affected individual: in cancer.

 

Cancers arise from a single cell that was mutated and many of the mutations are point mutations. Some are not. For instance, one form of leukemia is a translocation of part of the chromosome.

 

It is now thought that cancers are mutated adult stem cells. The progeny of those mutated cells do indeed "manifest itself in the affected individual", don't they?