Congenital lactase deficiency in humans is caused by very low activity of the enzyme lactase, resulting in individuals being unable to digest lactose in milk - Scottish Highers Biology - Question 12 - 2018
Question 12
Congenital lactase deficiency in humans is caused by very low activity of the enzyme lactase, resulting in individuals being unable to digest lactose in milk. This i... show full transcript
Worked Solution & Example Answer:Congenital lactase deficiency in humans is caused by very low activity of the enzyme lactase, resulting in individuals being unable to digest lactose in milk - Scottish Highers Biology - Question 12 - 2018
Step 1
Name a gene mutation which causes a frame-shift.
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Answer
A deletion or insertion in the DNA sequence can cause a frame-shift mutation.
Step 2
Describe the effect of this frame-shift mutation on the lactase gene.
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Answer
The frame-shift mutation will alter all the codons, or base sequences, downstream of the mutation. This means that the entire reading frame is shifted, resulting in a completely different translation from the original sequence.
Step 3
Effect on structure of lactase.
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Answer
Due to the altered reading frame, the resulting structure of lactase will be significantly changed. The amino acids synthesized after the mutation will differ, potentially leading to a nonfunctional enzyme.
Step 4
Suggest why this may lead to more lactase enzyme being produced.
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Answer
If mutations occur in the regulatory sequences, the gene may be permanently switched on, leading to increased transcription of the lactase mRNA and subsequently more lactase enzyme being produced.
Step 5
State the term which describes this change in gene frequency when a small population of individuals breaks away from a larger population.
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This phenomenon is known as the founder effect or genetic drift.
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