Mutations and examples

[Miss R]

Hi,

 

Can anyone give me an example of each of the type of mutations. I have tried researching but im getting more and more confused.

 

Insertions

Missense mutation

Nonsense

Splice site

 

I know the diseases with deletions and microdeletions, and repeat amplifications, but not sure about these ones.

 

Also, would you consider huntington disease as a trinucleotide repeat amplification or insertion/deletion ?

 

Please help !

[chadn737]

Try explaining what you think these different mutation types are and I will help you with any misunderstandings.

 

You can think of an insertion as the opposite of a deletion.

 

Missense and nonsense mutations are actually classified both as nonsynonymous mutations, its just that what they change the codon to differes.

 

A splice site has to do with its effect on alternative splicing.

 

As far as huntington's...heres your hint, some types of mutations are subcategories of other types and can be classified in more than one way.

 

Those are all the more hints I am willing to give without further input from you.

[Miss R]

Ok,

 

insertions are when a base is added to a sequence, is also known as frameshift mutation because they can change the whole codon, I think.

 

Missense is when a codon changes to a different one, I actually got an example of this , it would be sickle cell anaemia. as the code changes.

 

nonsense is when the code changes to a stop codon and thus early termination of a protein etc cant find any disease example of this...

 

Splice site mutation currently having problem understanding this one despite reading about it

 

That's what I thought with Huntington disease, so then it can be categorised under both repeat amplification and insertion mutations?

 

Let me know what you think

[chadn737]

You are right about what an insertion, missense, and nonsense mutations are.

 

If you are looking for an example of a nonsense mutation, try searching for diseases similar to sickle cell anemia centered in the mediteranean. The first thing that comes to mind is such an example. Then let me know what you find.

 

So with a splice mutation. Are you familiar at all with what an exon and intron is? Exons are the coding part. Introns can be thought of a "spacer" between two exons in a very simplistic sense. Its a lot more complicated than that, but in understanding this, just think of it as a spacer separating two exons. In order to create the final coding sequence, you have to cut out the intron between the two exons and combine the two exons into one piece. Now there are sequences in the intron that tells the cell that this is where the intron starts and stops and how it should be cut out. If you had a mutation in one of these sites, what do you think would happen?

 

Yes. Technically the trinucleotide repeat of Huntington's is a form of insertion. However, be careful, sometimes people make a distinction between the two.

[Miss R]

Beta- thalassemia ? this is the one disease I could find under nonsense mutation and is centred in the Mediterranean. I looked at Tay Sach's but that's prevalent in Jewish community and is commonly due to insertion mutation.

 

Would it result in production of a faulty protein ? I am not quite sure