Microevolution & Population Genetics

What is the biological definition of evolution?

A change in allele or genotype frequencies in populations over time.

Differentiate Microevolution and Macroevolution.

Microevolution: Changes within species (e.g., changes in allele frequencies). Macroevolution: Changes between species (large-scale evolutionary change).

What is an adaptive radiation?

The rapid diversification of organisms from an ancestral species when environmental change makes new resources or challenges available, opening new environmental niches.

Provide a historical public health example of rapid microevolution.

The evolution of antibiotic resistance in Staphylococcus strains against Penicillin (e.g., resistance increased from 14% to over 50% between initial use and 1950).

What is a "population" in the context of genetics?

A group of individuals of the same species that live in the same area, interbreed, and produce fertile offspring.

Define the gene pool.

The sum of all alleles at all gene loci in all individuals within a population. It characterizes a population’s genetic makeup.

What are the two main sources of new genetic variation in a population?

1. New alleles (from germ-line mutations which occur in reproductive cells).

2. Recombination (from crossing over, independent assortment, and random fertilization).

Why is the genetic component of phenotypic variation essential for evolution?

Evolution (specifically natural selection) can only act on heritable variation, which is the genetic component of the phenotype.

What is Qualitative Variation?

Characteristics with distinct states (e.g., 'yes' or 'no' presence of a trait), often described as polymorphisms.

What is Quantitative Variation?

Characteristics with a range of variation (e.g., height) that are typically controlled by multiple genes.

State Mendel’s Law of Segregation.

Organisms carry two alleles per trait, which segregate (separate) during gamete formation so each gamete carries only one allele per trait.

State Mendel’s Law of Independent Assortment.

The inheritance of one trait is independent of the inheritance of another, provided the genes for the traits are on different chromosomes.

How are genotype and allele frequencies calculated from a population sample? (Using A and a alleles)

Genotype Frequency: Count the number of individuals with a specific genotype (e.g., AA) and divide by the total number of individuals. Allele Frequency (e.g., A): Sum the number of A alleles (2 per AA individual + 1 per Aa individual) and divide by the total number of alleles (2 * total individuals).

What is the "Best" way to assess genetic variation?

Measure genetic variation directly using methods like DNA sequencing (e.g., PCR-based high-throughput sequencing).