Why does a mutation in DNA replication have a more dire effect than in ...

[discowisco]

Why does a mutation in DNA replication have a more dire effect than in trancription?

I thought DNA replication polymerase have exonuclases to fix errors while rna polymerases don't?

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[ashtonjam]

If there is a DNA mutation that goes uncorrected, it means all transcripts will have the mutation and lead to defective proteins.

If there is an RNA mutation, that's OK because RNA is designed to have a really short half life. There's lots of RNA transcripts at any given time, so a few of them being bad only leads to a few bad proteins.

 

[discowisco]

Yeah i understand that but the way the answer choices were given were:

Point mutation in transcription
Point mutation in translation

I just figured that an exonuclease could fix a point mutation

 

[ashtonjam]

It might be talking about a mutation that gets past the exonucleases. Do those answer choices have to do with replication?

 

[The Helpful Aye Aye]

Yeah i understand that but the way the answer choices were given were:

Point mutation in transcription
Point mutation in translation

I just figured that an exonuclease could fix a point mutation

You need to work on reading the question, since you understand the underlying concept. The language implies that the mutation was successful and isn't even close to as ambiguous as MCAT questions can be. Even if you reasoned that transcription might be worse, the instability of mRNA should have at least made you reconsider your answer.

 

[Helixkam]

It is because a messed up piece of RNA degrades and can only be translated out so many times into a faulty protein etc. But if a mutation slips into replication and is successful (have to assume that based on how the question is written) then you carry that mutation into every replication and transcription and translation leading to much more serious effects.

 

[ninjiliu]

Elaborating on what Helixkam is saying, mutated DNA can potentially affect an entire organism. Any protein synthesized from that DNA strand is essentially "mutated" and that strand of DNA could undergo translation multiple time. So instead of having a single messed up protein due to a translation error, you have a bunch of messed up proteins because the DNA is mutated. And the problem can worsen if the cell with the mutated DNA replicates.

 

[mehc012]

Elaborating on what Helixkam is saying, mutated DNA can potentially affect an entire organism. Any protein synthesized from that DNA strand is essentially "mutated" and that strand of DNA could undergo translation multiple time. So instead of having a single messed up protein due to a translation error, you have a bunch of messed up proteins because the DNA is mutated. And the problem can worsen if the cell with the mutated DNA replicates.

Yup...taken to extremes, it's the difference between cancer (or deformity if it occurs during development) and one bad protein in one cell.