A2 Cellular control?

Original post by ammzz

Is it just me or does everyone find this module EXTREMELY hard!!!
I cannot get my head around epistatis / gene loci / chi squares..

Does anyone have any recommended books (apart from the a2 heinemann OCR one) or websites?

If anyone has a spare moment, i would really appreciate someone to explain it in simple terms :frown:

In so much need of help!! thankyou!!!

Which part do you need the most help on?

Reply 2

OP

Original post by The Illuminati

Which part do you need the most help on?

In the OCR heinemann text book its spreads 3,4 (mutations), 11-16 (genetic diagrams/gene loci)
Also spread 18, (population genetics/hardy weinberg)
Sorry, that seems so much, i just cant get it into my head how to do it haha! :frown:

Reply 3

Tell me what parts of 2.1.3 (Mutations-1) you don't understand and I'll explain it as clearly as I can.

Reply 4

OP

I dont understand the terms silent mutation, nonsense and missense mutation.
Most of the time when i eventually understand the spread, its the exam Q's i get stuck on, im not very good at understanding them, but im the only person who can teach myself the technique i guess.

Reply 5

Original post by ammzz

I dont understand the terms silent mutation, nonsense and missense mutation.
Most of the time when i eventually understand the spread, its the exam Q's i get stuck on, im not very good at understanding them, but im the only person who can teach myself the technique i guess.

silent mutation is when the triplet code is different but it still corresponds to same amino acid because each amino acid has more than one triplet code that it corresponds to. Which is why there are 64 triplet codes but only 20 amino acids that our bodies can make.

a nonsense means that a stop codon appears prematurely so that the rest of the amino acids the the polypeptide can't be added as they haven't been coded for.

a missense means that the code corresponds to the wrong amino acid. So the protein doesn't work correctly due to the polypeptide chain containing the wrong amino acid.

these are all point mutations as they occur when one bases is replaced by another.

hope that's simple and makes sense....or helps in any way ................ :s-smilie:

Reply 6

OP

Original post by The Illuminati

silent mutation is when the triplet code is different but it still corresponds to same amino acid because each amino acid has more than one triplet code that it corresponds to. Which is why there are 64 triplet codes but only 20 amino acids that our bodies can make.

a nonsense means that a stop codon appears prematurely so that the rest of the amino acids the the polypeptide can't be added as they haven't been coded for.

a missense means that the code corresponds to the wrong amino acid. So the protein doesn't work correctly due to the polypeptide chain containing the wrong amino acid.

these are all point mutations as they occur when one bases is replaced by another.

hope that's simple and makes sense....or helps in any way ................ :s-smilie:

Yess that helps a lot thankyou!
Would i get a question that could simply ask me to define of of those types of mutations, or would it be more of an application question, just applying my knowledge of the meanings?

Reply 7

Original post by ammzz

Yess that helps a lot thankyou!
Would i get a question that could simply ask me to define of of those types of mutations, or would it be more of an application question, just applying my knowledge of the meanings?

you could get either type so I'd prepare for either type. They may describe a disease e.g. sickle cell and ask you what type of mutation it is I'd say its a missense point mutation (you could generalise and say point mutation but it's say missense just in case) as valine is inserted instead of glutamic acid.

Just think that changing one base can have a massive effect on the entire organism.

Reply 8