Modern Theory of Natural Selection

These flashcards cover key concepts regarding the modern theory of natural selection, its requirements, examples, and implications.

What are the three requirements for Natural Selection to occur?

1. Phenotypic variation 2. Fitness differs between phenotypes 3. Fitness differences are heritable.

What is the significance of a mutation in the enhancer region of the gene MCM6?

It confers lactase persistence in humans.

What is industrial melanism in the peppered moth?

It is the first example of evolution by natural selection directly observed in the wild, where phenotypic distribution changed due to pollution.

How can the strength of natural selection be quantified?

By measuring how fit a genotype must be compared to competing genotypes to spread to fixation over generations.

What does the term 'hitchhiking' refer to in the context of genetic selection?

It refers to the process where a beneficial mutation spreads to fixation along with a nearby deleterious mutation, eliminating polymorphism.

What does the 'selection coefficient' (s) represent?

It is the increase (or decrease) in fitness caused by carrying a copy of the allele.

What is the example of a fitness trade-off related to antibiotic resistance?

Antibiotic resistance carries a fitness cost; in the absence of antibiotics, resistant mutants grow more slowly than susceptible mutants.

What are some examples of genes in humans under recent positive selection?

LCT (lactase persistence), G6PD (glucose-6-phosphate dehydrogenase), CYP3A5 (cytochrome P450), ADH1B (alcohol dehydrogenase), HBB (beta-globin), CKR5 (chemokine receptor).

What is meant by 'mutation-selection balance'?

It explains the persistence of heritable diseases despite purifying selection, as deleterious alleles can never be eliminated completely from the population.

What is the evolutionary explanation for design flaws in organisms?

Design flaws arise because all species are modified from pre-existing species, leading to compromises that wouldn't occur if each species could be engineered from scratch.