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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 for milk likely provided a significant nutritional advantage to humans who could consume lactose throughout their lives. Individuals with the lactase persistence (LP) allele were better able to digest milk, which meant they could access a valuable food resource. As these individuals survived and thrived, reproducing with others who also had LP, the frequency of the allele increased within the population. Over generations, natural selection would favor those with the LP allele, as they would have a higher survival rate and reproductive success due to the benefits of milk consumption.
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 a population of humans began farming cattle and consumed their milk, the selection pressure for lactase persistence would become significant. Those individuals who possessed the LP allele would have a dietary advantage, allowing them to utilize milk as a food source. As these advantageously adapted individuals reproduced, the LP allele would be passed on to their offspring. The rapid increase in the number of individuals demonstrating LP would result from the increased reproductive success of those with the allele, leading to a higher proportion of the population exhibiting lactase persistence in subsequent generations.