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Lactose is the main sugar in milk and is hydrolysed by the enzyme lactase - AQA - A-Level Biology - Question 9 - 2018 - Paper 1
Question 9
Lactose is the main sugar in milk and is hydrolysed by the enzyme lactase. Lactase is essential to newborn mammals as milk is their only source of food. Most mammals... show full transcript
Worked Solution & Example Answer:Lactose is the main sugar in milk and is hydrolysed by the enzyme lactase - AQA - A-Level Biology - Question 9 - 2018 - Paper 1
Step 1
Describe how farming cattle as a source of milk could have led to an increase in LP.
Answer
Farming cattle provided a consistent source of milk for certain human populations. This availability of milk would lead to a selective pressure favoring individuals who could digest lactose into adulthood. As these individuals became more successful at surviving and reproducing due to the nutritional benefits gained from consuming milk, the frequency of the lactase persistence allele would increase in the population. Consequently, over generations, more individuals would inherit this advantageous trait, resulting in a higher prevalence of lactase persistence (LP).
Step 2
Use the information provided to explain why the number of people showing LP would rapidly increase once selection for this condition had been established.
Answer
Once the selective pressure for lactase persistence was established, any individuals carrying the dominant allele for LP would have a reproductive advantage. As these individuals survive better and reproduce more successfully than those who do not possess the allele, the allele would be passed on to the next generation. This process, driven by natural selection, would lead to a rapid increase in the proportion of the population with LP as generations progress, particularly in populations that have a strong reliance on dairy products.