Assuming one with AD died in 2014, calculate the annual percentage increase in AD cases in America for 2014 (lines 2–4) - AQA - A-Level Biology - Question 10 - 2017 - Paper 1

Donepezil is a medication that inhibits the enzyme acetylcholinesterase, which is responsible for breaking down acetylcholine in the synaptic cleft. By blocking this enzyme, donepezil increases the concentration of acetylcholine available to bind to receptors on the post-synaptic neuron. This improved availability can enhance communication between nerve cells, as acetylcholine plays a crucial role in transmitting signals that facilitate nerve impulse generation, leading to improved cognitive function and memory in patients with Alzheimer’s.

1. Isolation and Inbreeding: Yaramul is an isolated town, leading to lower genetic diversity among its inhabitants. This isolation increases the likelihood that recessive mutations, like E280A, are passed on due to limited gene pool mixing.

2. Founder Effect: If the E280A mutation first arose in a small founding population, it may have been carried through generations, resulting in a higher frequency of this mutation in subsequent generations due to its persistence in the limited gene pool.

Natural selection may not have reduced the frequency of the E280A mutation due to the possibility that carriers of this mutation often survive to reproductive age and pass the mutation onto the next generation. Additionally, the mutation may confer some beneficial factors in the specific environmental context of Yaramul, balancing the potential disadvantages associated with Alzheimer's Disease.

One possible reason for the variation in the age of onset of AD associated with the E280A mutation could be genetic background. Different individuals may carry varying combinations of other genetic factors or mutations that can either speed up or delay the onset of the disease, leading to differences in age at which symptoms manifest.

The discrepancy between the number of detected E280A mutations (75) and potential AD cases (74) might arise from factors such as incomplete penetrance, where not all individuals with the mutation develop AD. Additionally, there may be other environmental or lifestyle factors influencing whether mutation carriers express symptoms of the disease, contributing to the observed difference in numbers.

A DNA probe for the mutated triplet may not have been suitable due to the possibility of non-specific binding or because the mutated triplet may be common in other genes, which could lead to false positives. Moreover, if the mutation is rare in the population, the sensitivity of the probe might be inadequate to detect it reliably, resulting in missed cases.