Naked Science Forum

Life Sciences => Cells, Microbes & Viruses => Topic started by: Kashefa Farooqui on 24/11/2010 07:30:03

Title: How do mutations happen?
Post by: Kashefa Farooqui on 24/11/2010 07:30:03

Kashefa Farooqui  asked the Naked Scientists:
   
Hi Chris

Love your show (http://www.thenakedscientists.com/HTML/podcasts/) on Five Live. I have a question that's been puzzling me recently. At the molecular level how does mutation occur in the gene? How does say exposure to radiation cause a point mutation on the chromosome?

Regards
Kashefa

What do you think?

Title: How do mutations happen?
Post by: SteveFish on 25/11/2010 00:54:42

A mutation occurs when the nucleotide sequence along a chromosome is permanently broken or altered by radiation with high enough energy (ultraviolet light or greater) to break covalent bonds, by a mutagenic chemical, or by some natural cellular processes.

Title: How do mutations happen?
Post by: 5nutjob on 26/11/2010 19:25:03

Viral mutation should not be ignored;- as these 'buggers' are simply most adept @ the re-sequencing act.

Title: How do mutations happen?
Post by: CliffordK on 01/12/2010 07:01:16

A typical chromosome has between 50,000,000 and 250,000,000 base pairs.

DNA Transcription errors can spontaneously occur during replication.  While your body is constantly subjected to "background radiation", it is quite possible that these errors will crop up independent of the radiation.

The cells have mechanisms to repair such transcription errors, but they are not perfect, so mutations will periodically spontaneously occur.

Another problem is that the proteins can not transcribe to the end of the genes...  so telomeres of essentially null base pairs are appended to the ends.  If these telomeres aren't maintained, then with each successive replication the DNA gets shorter until genetic regions start getting gobbled up and mutations start occurring.

As mentioned above, viruses also have to replicate their DNA or RNA genes.

A special class of viruses called retroviruses carry RNA genes which they transcribe into DNA genes, and then have them transcribed back into RNA.  Their retro transcription mechanism is notoriously error prone which causes a very high spontaneous mutation rate within a single host.  This is one of the reasons that HIV/AIDS is so difficult to combat.  The gene transcription errors and spontaneous mutations becomes a virulence mechanism.