**Question:** “Founder effect” describes the distribution of diseases on the basis of

A. population genetics
B. geographical location
C. socio-economic status
D. historical events

**Core Concept:** The founder effect is a biological phenomenon that occurs when a small group of individuals establish a new population, leading to a change in the gene pool compared to the original population. This can result in the prevalence of certain genetic traits or diseases in the new population due to reduced genetic diversity.

**Why the Correct Answer is Right:** The correct answer, A. population genetics, is related to the genetic makeup and distribution of diseases within populations. When a small group of individuals from a larger population founds a new one, the genetic diversity gets reduced, leading to the increased prevalence of certain genetic traits or diseases in the new population.

**Why Each Wrong Option is Incorrect:**

B. Geographical location (option B) is not the primary cause of the founder effect. While geographical factors may influence disease prevalence due to founder effect, the core cause lies in the genetic changes occurring within the new population.

C. Socio-economic status (option C) plays a role in disease distribution but is not the primary cause of the founder effect. Socio-economic factors can influence disease prevalence, but the genetic changes resulting from the founder effect are the fundamental aspect of the question.

D. Historical events (option D) may contribute to the founding of new populations and subsequent founder effects, but the core concept being tested is the genetic changes caused by the founder effect itself.

**Clinical Pearl:** The founder effect is important to understand when assessing disease prevalence in small populations, such as indigenous communities or isolated regions. Understanding the genetic basis of disease distribution can help guide public health strategies and disease prevention measures.

**Correct Answer:** A. Population genetics