Heritability and Hardy-Weinberg Equilibrium Flashcards

Vocabulary flashcards covering phenotypic variation, heritability concepts, high/low fitness trait examples, and the principles and mathematical foundations of Hardy-Weinberg equilibrium.

Heritability ($h^2$)

A population-wide estimate describing the proportion of total phenotypic variation in a population that is attributable to genetic differences among individuals, mathematically defined as $h^2 = \frac{V_g}{V_p}$ and ranging from $0$ to $1$.

Total Phenotypic Variation ($V_p$)

The total observed variation in a trait across a population, which equals the sum of variation due to genetic differences ($V_g$) and variation due to environmental differences ($V_e$).

Inherit vs. Heritability

'Inherit' is an individual-level measure describing the transmission of alleles from parent to offspring, whereas 'heritability' is strictly a population-level estimate that cannot be measured for an individual.

Heritability of High Fitness Adaptations

Essential traits crucial for survival (such as genes that construct the heart or brain) generally have a heritability near $0$ because purifying selection eliminates harmful mutations, leaving individuals as essential genetic clones for those genes.

Human Height Heritability

The highest value trait for heritability measured in humans, estimated between $0.75$ and $0.88$, indicating that height variation in a population is strongly controlled by genetic differences rather than fitness selection.

Character

An alternative scientific term used synonymously with 'trait' when evaluating phenotypic variation in a population.

Hardy-Weinberg Equilibrium

A state in population genetics where allele and genotype frequencies remain constant generation after generation, serving as a null model indicating that a population is not evolving.

Primary Function of Hardy-Weinberg

To predict expected genotype frequencies in the next generation based strictly on actual observed allele frequencies.

Allele Frequency Equation ($p + q = 1$)

The formula establishing that in a two-allele genetic system, the frequency of the dominant allele ($p$) plus the frequency of the recessive allele ($q$) must sum to $1$ ($100\%$ of the population's alleles).

Hardy-Weinberg Equation ($p^2 + 2pq + q^2 = 1$)

The mathematical formula predicting expected genotype frequencies, where $p^2$ represents homozygous dominant individuals, $2pq$ represents heterozygous individuals, and $q^2$ represents homozygous recessive individuals.

Mathematical Origin of $2pq$

The factor of two in the Hardy-Weinberg equation representing the two distinct mathematical pathways to form a heterozygous genotype: drawing a dominant allele followed by a recessive allele ($pq$), or a recessive allele followed by a dominant allele ($qp$).

Assumptions of Hardy-Weinberg Equilibrium

The set of conditions required for a population to remain non-evolving, including random mating, no natural selection, infinite population size (no genetic drift), no gene flow, and no mutations.