Angel4life
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#1
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#1
explain how a single base change in dna can lead to a non functional protein
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Marsharko
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#2
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#2
Primary structure of proteins is the sequence of amino acids.

Sequences of amino acids are coded for by the sequence of bases. If a mutation changes a base, then it can change the corresponding amino it codes for. This leads to changes in the primary structure.

Changes in primary can affect how the protein folds in secondary and tertiary structure regarding ionic and disulfide bridges.

End result is a protein with an altered tertiary structure (denatured) that prevents it from doing its function.
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Angel4life
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#3
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#3
(Original post by Marsharko)
Primary structure of proteins is the sequence of amino acids.

Sequences of amino acids are coded for by the sequence of bases. If a mutation changes a base, then it can change the corresponding amino it codes for. This leads to changes in the primary structure.

Changes in primary can affect how the protein folds in secondary and tertiary structure regarding ionic and disulfide bridges.

End result is a protein with an altered tertiary structure (denatured) that prevents it from doing its function.
thank you also is it right to include that changes to active site prevents enzyme substrate complexes thus protein non functional
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clueIxss
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#4
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#4
(Original post by Angel4life)
thank you also is it right to include that changes to active site prevents enzyme substrate complexes thus protein non functional
Hi there. Different person, but I would only include this as an example, because it isn’t specifically asking about enzymes (not all proteins are enzymes after all!). Otherwise, you may not be answering the question directly according to the mark scheme. I could be wrong and they could accept it because enzymes are proteins, but Marsharko provides a perfectly good answer without the need to write about enzymes. Every protein relies on its specific 3D structure to do its job, and changes in primary structure affecting protein folding will therefore be possibly detrimental for any protein (think of all the other types, like proteins embedded in cell membranes for example). Hope this helps!
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Reality Check
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#5
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#5
(Original post by Angel4life)
thank you also is it right to include that changes to active site prevents enzyme substrate complexes thus protein non functional
Well that would only be relevant if the point mutation (a) happened in a region of the chain which comprised the active site and (b) the point mutation actually made a material difference, which it might not necessarily.

A good answer would make clear that the DNA point mutation results in a change in the mRNA which acts as the script for the protein synthesis. In other words, don't just jump from DNA to protein without showing you know the intermediate step!

It would be good to also mention that a point mutation could result in turning a normal codon into a stop codon, resulting in a truncated, non-functioning protein (a 'nonsense' mutation). For instance, a DNA point mutation leading to an mRNA codon change from CGA to UGA. Whereas CGA codes for arginine, UGA is a STOP codon. You can see what the consequence of such a point mutation would be.
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Angel4life
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#6
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#6
(Original post by clueIxss)
Hi there. Different person, but I would only include this as an example, because it isn’t specifically asking about enzymes (not all proteins are enzymes after all!). Otherwise, you may not be answering the question directly according to the mark scheme. I could be wrong and they could accept it because enzymes are proteins, but Marsharko provides a perfectly good answer without the need to write about enzymes. Every protein relies on its specific 3D structure to do its job, and changes in primary structure affecting protein folding will therefore be possibly detrimental for any protein (think of all the other types, like proteins embedded in cell membranes for example). Hope this helps!
thank you man
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Angel4life
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#7
Report Thread starter 1 year ago
#7
(Original post by Reality Check)
Well that would only be relevant if the point mutation (a) happened in a region of the chain which comprised the active site and (b) the point mutation actually made a material difference, which it might not necessarily.

A good answer would make clear that the DNA point mutation results in a change in the mRNA which acts as the script for the protein synthesis. In other words, don't just jump from DNA to protein without showing you know the intermediate step!

It would be good to also mention that a point mutation could result in turning a normal codon into a stop codon, resulting in a truncated, non-functioning protein (a 'nonsense' mutation). For instance, a DNA point mutation leading to an mRNA codon change from CGA to UGA. Whereas CGA codes for arginine, UGA is a STOP codon. You can see what the consequence of such a point mutation would be.
thanks
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