Shawaiz121
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One of the enzymes involved in glycogen synthesis is glycogen synthase. The glycogen synthase in muscle cells is known as GYS1.
There are a number of known mutations for GYS1.

Outline how a mutation in GYS1 can lead to the formation of an altered polypeptide where one amino acid is replaced by a different amino acid.


Can explain how to answer this? Much appreciated
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ImReady!
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what exam board is this for?
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Shawaiz121
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(Original post by ImReady!)
what exam board is this for?
Cambridhe CIE . 9700. Do you know how to answer this?
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macpatgh-Sheldon
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Hi once again,

Let me show you in a way that will help you answer similar BUT NOT IDENTICAL Qs in future:-

I. First work out what part(s) and sub-part(s) of syllabus you are being tested on:- here A) DNA structure/protein synthesis/triplet code
B) the process of mutation/its different types. {you DO NOT really need to know about glycogen synthesis LET ALONE about GYS1, although of course it is important to know about polysaccharides for other Qs).

II. Then try to read the examiner's mind AND WORK OUT what each mark (total given in brackets) is for:-

PROBABLE MARK SCHEME:

a) One amino acid coded for by 3 nucleotide bases - triplet code in DNA -----> mRNA
b) if one base is i) substituted by another -----> wrong triplet code
c) this means wrong amino acid made

(I would expect that you will not get ANY marks for deletion, insertion of a base because this would change a number of amino acids (distal to the mutation) WHEREAS Q says "where one amino acid is replaced....................................".

Hope this helps!
M
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Shawaiz121
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(Original post by macpatelgh)
Hi once again,

Let me show you in a way that will help you answer similar BUT NOT IDENTICAL Qs in future:-

I. First work out what part(s) and sub-part(s) of syllabus you are being tested on:- here A) DNA structure/protein synthesis/triplet code
B) the process of mutation/its different types. {you DO NOT really need to know about glycogen synthesis LET ALONE about GYS1, although of course it is important to know about polysaccharides for other Qs).

II. Then try to read the examiner's mind AND WORK OUT what each mark (total given in brackets) is for:-

PROBABLE MARK SCHEME:

a) One amino acid coded for by 3 nucleotide bases - triplet code in DNA -----> mRNA
b) if one base is i) substituted by another -----> wrong triplet code
c) this means wrong amino acid made

(I would expect that you will not get ANY marks for deletion, insertion of a base because this would change a number of amino acids (distal to the mutation) WHEREAS Q says "where one amino acid is replaced....................................".

Hope this helps!
M

I have some idea of what you are taking about. But can you give more details please.
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macpatgh-Sheldon
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Hi,

Take an analogy:-

Suppose you have a necklace of coloured beads: Red (R), Green (G) and Blue (B)

The order of beads in necklace is: GRBBBRGBGGBRRG (14 beads total) - yeah?

Imagine that each possible Two beads in order represent a fruit (e.g.) as below:-

GR = apple
GB = pear
GG = peach
BG = banana
RG = plum
RR = grape
BB = passion fruit
RB = pineapple
BR = pomegranate

There are 3^2 = 9 possibilities (in the case of triplet code out of 4 bases there are 4^3 = 64 choices.

The necklace you have is GR BB BR GB GG BR RG (copied from above but in pairs in same order) representing: apple, passion fruit, pomegranate, pear, peach, pomegranate, plum IN ORDER - OK, with me?

If one bead is replaced by different one e.g. if 5th bead becomes Red instead of Blue THE ONLY FRUIT THAT WILL CHANGE is the third one from pomegranate (BR) to grape (RR). NOTHING ELSE WILL CHANGE!

HOWEVER, if you say ADD A BEAD, say Green one to after the 6th bead, you now have: GRBBBRGGBGGBRRG

If you split into your parts of two each you have: GR BB BR GG BG GB RR G

The order of fruits represented now is: apple, passion fruit, pomegranate, peach, banana, pear, grape AND ONE EXTRA BEAD (Green).

DO YOU SEE THAT ADDING A BEAD CHANGES ALL THE FRUITS AFTER THE POSITION WHERE YOU ADDED IT, in this case ALL FRUITS after the first pomegranate? This is what happens with an INSERTION type of mutation (YOUR fruits here are your amino acids and the different coloured beads (we only have 3 here) are your nitrogen bases (of which there are four) in DNA.

SIMILARLY, if we were to remove one bead completely (called a DELETION type of mutation) you will of course ALTER THE WHOLE AMINO ACID SEQUENCE after the deletion, agreed.

So, since your Q asks for a change in ONE amino acid, you cannot have insertion or deletion in your answer.

I hope this makes it crystal clear.

M
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macpatgh-Sheldon
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Shawaiz121


Check out above young man! Go through it carefully, step by step - you will get the hang of it!
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