Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: EvaH on 19/06/2020 12:54:38
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Paul wants to know:
As different generations happen, are modifications on chromosomes likely to be down lower on a chromosome or could modifications occur all over a chromosome?
What do you think?
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Mutations can occur for a variety of reasons:
- Disruption due to subatomic particles from radioactive decay or cosmic rays.
- Disruption due to ultraviolet light
- Disruption due to reactive oxygen species from cell metabolism
- Errors in correcting one one of the above effects
- Disruption due to copying errors during cell replication
- Retroviruses or "jumping genes" inserting themselves into the genome
All of these effects could (in theory) impact any part of any chromosome, in any generation
- Whether the cell survives the mutation depends on:
- what the mutation is (some mutations are just different ways of spelling the code for the same protein)
- which gene (and which part of it) are mutated. Most genes have a "spare" copy on the other chromosome
- whether the cell "thinks" it has successfully repaired the mutation. If the cell "knows" that it has failed, it will normally commit suicide (apoptosis), rather than allow the cell to become potentially cancerous.
- It's just highly unlikely that a mutation would hit exactly the same spot as a previous mutation, to undo it.
See: https://en.wikipedia.org/wiki/Mutation#Causes
down lower on a chromosome
It's unclear to me what this phrase means.
At the level of a single chromosome, "up" and "down" don't mean very much.
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It's possible that some bits of some genes are (when the gene is folded) are buried in the middle, and thus less susceptible to some mutagens- eg UV light.
Not sure that counts as "low down".
Incidentally, not all chemical mutagens are reactive oxygen species.
Alkylating agents (among others) are also mutagens.