Genetic Drift Simulation – Code Explained

This simulation visually shows how allele frequencies change over time due to genetic drift. Here’s how the simulation works:

1. Population Initialization

• Users select population size and the starting percentage of allele “A” (red) using sliders.
• The rest of the population has allele “a” (blue).

2. Next Generation Logic

• Each generation is formed by randomly selecting alleles from the current gene pool.
• This random sampling simulates genetic drift (random chance) affecting allele frequencies.
• Allele frequencies are tracked and visualized on a line graph (using Chart.js).

3. Special Features

• Bottleneck Effect: Temporarily shrinks the population, making random changes more extreme.
• Founder Effect: Starts the simulation with a small sub-population, mimicking migration.
• Fixation Detection: Alerts when only one allele remains in the population (0% or 100%).

4. Controls

• Pause/Resume: Allows user to stop or continue simulation.
• Reset: Restarts the simulation using current settings.
• Alleles are displayed below the chart as red (A) and blue (a) dots.

🔬 What is Genetic Drift?

Genetic drift is a random change in allele frequency in a population. Unlike natural selection, it is not influenced by fitness. It’s especially significant in small populations.

🎯 Key Features

• Random, chance-driven changes
• Can result in allele fixation or loss
• More noticeable in small populations

🌪️ Types of Genetic Drift

1. Bottleneck Effect

A sharp reduction in population due to disasters (flood, disease, etc.) causes dramatic allele frequency changes.

Example: Only a few cheetahs survive a natural disaster, reducing genetic variation drastically.

2. Founder Effect

A few individuals from a population start a new population in a new place. Their alleles may not represent the original population well.

Example: A few beetles float to a new island and begin a colony with limited genetic variation.

📉 Genetic Drift in Action

This graph below shows how the frequency of allele A (red) may fluctuate randomly across generations in a small population.

⚡ Why It Matters

• Reduces genetic diversity
• Can lead to harmful alleles becoming fixed
• Plays a key role in evolution, especially in isolated or endangered populations