Covers genetic drift and its sub-forms, the bottleneck and founder effects, with the Ashkenazi Jewish population given as a founder example. It then turns to gene flow through migration, natural selection with a relative fitness and selection coefficient measure, and the Duffy null allele and vitamin D skin examples. Mutation rates, the combined action of mutation and selection, and nonrandom mating close the note.
Inside: 4 sections · 4 labelled pictures · 8 min
Topic 37 of 64 in the MU Sofia syllabus for Biology (Dental Medicine, Year 1). The free AceMed note covers it in 4 sections, about 1,163 words (8 min of reading).
In this note
Genetic Drift Explained
Bottleneck Effect: A Type of Genetic Drift
Founder Effect: Another Flavor of Genetic Drift
Combined action of mutation and selection
Genetic Drift Explained
What is Genetic Drift?
Basic Idea: Genetic drift is like rolling dice to decide which genes get passed on. Sometimes, by pure chance, certain genes become more common or disappear entirely in a group of living things over time.
Why It Matters More in Small Groups: In a tiny population, just like in a small dice game, chance has a bigger role. A few unusual rolls can change things a lot.
Key Points:
Random Changes: It's all about random changes, not about getting better or adapting to the environment.
Big Effects in Small Populations: It's a big deal in small groups where chance plays a bigger role.
Can Lead to Loss of Genes: Sometimes, a gene can disappear entirely from a small group due to random chance.
Bottleneck Effect: A Type of Genetic Drift
What is the Bottleneck Effect?
Sudden Drop in Numbers: Imagine something drastic happens (like a natural disaster) and suddenly there are very few individuals left. The genes of those who survive (by luck) will shape the future group.
Random Survival: Who survives is random. It's not about being the strongest or the smartest; it's about luck.
Lab Example: If you randomly pick a few beans from a bag, you might not get an even mix. It's similar to what happens in nature during a bottleneck.
Real-World Impact:
Humans Have Faced It: Human history has seen bottleneck events, where our numbers have dramatically decreased, affecting our genetic diversity.
Continue reading free
The whole note, all 4 sections, is free with an AceMed account. Premium adds flashcard recall, highlights and Ask AI.
