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    Hi! I missed 2 lessons in a row in Biology so my teacher has sent me the work through so I can catch up.

    He told me to use the notes from someone in my class, but I don't really get along with any of them so I was wondering if you could help me. I've already looked at the study resources and can't seem to find this:

    What are mis-sense mutations, silent mutations, and nonsense mutations? How do they come about and how do their affects differ?

    Thanks
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    http://www.thealevelbiologist.co.uk/gene-mutation

    ^^ try the above.
    What exam board are you following by the way?
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    (Original post by Hajra Momoniat)
    http://www.thealevelbiologist.co.uk/gene-mutation

    ^^ try the above.
    What exam board are you following by the way?
    Thank you it's AQA
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    O wow. Ive looked on the spec and it doesn't mention any of this. On top of this ive never heard of these terms before from my teacher and past papers. Im shocked xD
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    Np too
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    (Original post by Hajra Momoniat)
    O wow. Ive looked on the spec and it doesn't mention any of this. On top of this ive never heard of these terms before from my teacher and past papers. Im shocked xD
    I know, I looked in the revision guide and couldn't see it either. Sometimes my teacher likes to add other elements into our learning though so we understand the wider picture
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    I guess so. What I say is don't let it make you more stressed. If youre happy with learning extra info then its your choice.

    On a website called Get Revising I have resources that I have made based on AS and A2 Biology spec from AQA. Go on to the link below, make an account which is free and then message me (my name on get revising is the same as the one on here). This is so you can go into the 'sent messages' and click on my name which will come up on the right in blue for you to click on and all my reosurces will come up. The only resource I haven't uploaded is investigating biodiversity.

    https://getrevising.co.uk/
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    (Original post by Hajra Momoniat)
    I guess so. What I say is don't let it make you more stressed. If youre happy with learning extra info then its your choice.

    On a website called Get Revising I have resources that I have made based on AS and A2 Biology spec from AQA. Go on to the link below, make an account which is free and then message me (my name on get revising is the same as the one on here). This is so you can go into the 'sent messages' and click on my name which will come up on the right in blue for you to click on and all my reosurces will come up. The only resource I haven't uploaded is investigating biodiversity.

    https://getrevising.co.uk/
    I don't really have a choice tbh as I'll get in trouble if I don't do the work! I will only revise the specification for my exams though
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    (Original post by Amefish)
    I don't really have a choice tbh as I'll get in trouble if I don't do the work! I will only revise the specification for my exams though
    Yh , well if you need any help with anything I will try my best to hep you
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    (Original post by Amefish)

    What are mis-sense mutations, silent mutations, and nonsense mutations? How do they come about and how do their affects differ?

    Thanks
    It's really quite simple to understand if you have a good grasp of how DNA codes for proteins. You should know that each amino acid is coded for by one or more three-base codons. For example, ATG codes for methionine etc. Also remember that there are a number of codons that also code for a stop. The associated tRNA carries release factors instead of an amino acid so when the ribosome reads that it causes the protein chain to release from the ribosome and that's the end of making that chain.

    A mis-sense mutation is when one of the DNA bases changes so the new codon codes for a different amino acid. For example, if ATG gets mutated to AAG, then that codon will code for lysine instead of methionine.

    A non-sense mutation is when one of the DNA bases changes so that the new codon codes for a stop codon. For example, if AAG gets mutated to TAG, then there will be a stop instead of lysine and the peptide will end early. This has very severe consequences and results in a shortened non-functional protein that is often actually degraded by special enzymes in a process called nonsense-mediated decay.

    Another type of mutation you should know about is a frame shift. This is when you have an insertion or deletion (sometimes called 'indel') that changes the reading frame of downstream codons. For example if you have a sequence ATG-CAG-AAG-CCA, and then get an insertion in the first codon it will become AAG-GCA-GAA-GCC... so the code changes from Methionine-Glutamine-Lysine-Proline to Lysine-Alanine-Glutamic acid-Alanine. In fact, usually with frameshifts you will get a premature stop codon somewhere down the line and this leads inevitably to nonsense-mediated decay as well.

    Silent mutations can be different things, but it is any mutation with no effect on phenotype. Either this could be because the mutation is in non-coding DNA or it could be a mutation of a codon that makes another codon that codes for the same amino acid. For example, GCA and GCC both code for alanine. Or it could changed to an amino acid with similar structure, or it just could be an amino acid in a protein linker where it doesn't matter what it is.
 
 
 
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