Hsc Trial Question

[--Daniel--]

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Hey guys
Ive been givin this question that is in my HSC trial and we havnt done the topic yet. The question is
DNA mutations were once thought to be extremely rare events. Outline reasons why the frequency of mutations were underestimated
The question is worth 3 marks and because i havnt done the topic yet I am having trouble finding answers.
Any help on what I can write for an answer would be great
Cheers Daniel

[xiao1985]

Hmmm interesting question... though rather out of context =/

One reason might be the good repair system our body has, which corrects most mutations in human genome. Therefore, mutation is thought to be a rare event.

[--Daniel--]

Thanx for that man. Any more ideas pplz, 2 more marks 2 go lol

[comman01]

Weird question...

u could also mention how the human genome project has given us a better understanding of the genome

and more generally, we've only begun to have a deeper understanding of how are genes work crossing over; base, substition mutations etc

(lol this is from the option right :S?)

those are my thoughts

[Survivor39]

Originally Posted by xiao1985

Hmmm interesting question... though rather out of context =/

One reason might be the good repair system our body has, which corrects most mutations in human genome. Therefore, mutation is thought to be a rare event.

To follow up on xiao's excellent point, another reason is that even though mutations may have occured, a genetic change may not always reflects a phenotypic change. For example, if a mutation occurs in a gene that encodes for amylase and that mutation is in a region that is not important for the function of that enzyme, then that enzyme would still be functional. So mutations may not have been realised.

[Survivor39]

Also, it is likely that our knoweldge of possible mutagens that causes mutations is limited. Therefore, we don't know that a lot of substances can potentially cause mutations.

[lyzzidc]

mutations were underestimated because they thought a mutation was only the x man style mutation. but really mutations are much simpler, e.g. the fact that we can drink milk past the age of 2 is a mutation, humans used to only be able to drink milk as babies.

[xiao1985]

hmm... I would think that mutation necessarily need to cause an error in the replication or expression of genes?

[bsurwald]

mutation numbers were underestimated firstly because of DNAs ability to self reair.
Often the mutations are recessive as they don't produce a functional proteind.
If a mutation occurs in a non-coding section of DNA it is likely that is will go unnoticed.
Some mutations to a single base can still give a codon that will give the same amino acid as the "unmutated" DNA during translation and therefore the effect of the mutation is not noticed.

That's all I can think of

[xiao1985]

well answered. admittedly, i overlooked several factors mentioned by you...

/cheers

[BlackJack]

Perhaps one more note not in relation to question:
- mutations in non-coding segments often still affects the outcome (!) because much of the regulation happens outside of the coding region. Do not be mislead as to the historical error that non-coding = useless. The timing and amount of expression, intron splicing, etc. are often coded around the portions that give the protein itself.
We don't notice these effects (as well as ones from many coding mutations) because they are often too small (individually,) to generate noticable physical effects.

This is part of the reasons why people have different tolerances to drugs, the genetic components of height and stature, some people break down alcohol more slowly than others, etc. Different amounts and minor changes in protein function, etc.