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mutation help please

Lactase persistence (the ability to continue producing lactase) is caused by a mutation in DNA. This mutation does not occur in the gene coding for lactase. Suggest and explain how this mutation causes LP.
Reply 1
Avatar for tocka90
tocka90
9
Mutation in promotor.
https://www.youtube.com/channel/UCQXFnAzACAnOAPVBv-QRNTQ
Look here for exam tips and revision videos made based on AQA new spec and PPQs.
thanks for the channel :smile:
But could you further explain this answer please?
Original post by tocka90
Mutation in promotor.
https://www.youtube.com/channel/UCQXFnAzACAnOAPVBv-QRNTQ
Look here for exam tips and revision videos made based on AQA new spec and PPQs.
Reply 3
Avatar for tocka90
tocka90
9
promoter is a region of DNA that initiates transcription of a particular gene. So if mutation occurs this particular gene cant be expressed.
Original post by anactualmess
thanks for the channel :smile:
But could you further explain this answer please?
but what gene is not being expressed?
Original post by tocka90
promoter is a region of DNA that initiates transcription of a particular gene. So if mutation occurs this particular gene cant be expressed.
There is an operon that is responsible for the expression for the lactase protein. An operon is a switch which can turn on and off deciding whether the protein is produced controlling lactase production. In this case the operon is mutated, so the operon is permanently ‘turned off’ meaning the protein is not expressed and therefore lactase is not produced (the operon has turned repressible). Hope this helps :smile:
Reply 6
Avatar for tocka90
tocka90
9
Mutation is taking place in promoter that normally would activate gene coding for lactase to be expressed. Mutated promoter = gene for lactase not expressed.
Original post by anactualmess
but what gene is not being expressed?
Thank you, but the mark scheme says. "Lactase gene continues to be transcribed/active"
Original post by _.angelica._
There is an operon that is responsible for the expression for the lactase protein. An operon is a switch which can turn on and off deciding whether the protein is produced controlling lactase production. In this case the operon is mutated, so the operon is permanently ‘turned off’ meaning the protein is not expressed and therefore lactase is not produced (the operon has turned repressible). Hope this helps :smile:
Mark scheme ". Lactase gene continues to be transcribed/active;" ?
Original post by tocka90
Mutation is taking place in promoter that normally would activate gene coding for lactase to be expressed. Mutated promoter = gene for lactase not expressed.
Reply 9
Avatar for vivik
vivik
8
hey sorry i dont know the answer but where's this question from?
Yes as people have been saying there is a mutation in the promoter region (where RNA polymerase should bind) so becuase of this mutation the suggestion is it makes it easier for RNA polymerase to bind to the DNA but not the gene (the part that is coding for mRNA) itself. Therefore RNA polymerase will transcribe the gene for the lactase enzyme.


I am a A-level biology teacher with molecular biology degrees.
Original post by anactualmess
Thank you, but the mark scheme says. "Lactase gene continues to be transcribed/active"

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