Hardy-Weinberg principle

The Fundamental Equations:

p + q = 1

p² + 2pq + q² = 1

• p = frequency of the dominant allele
• q = frequency of the recessive allele
• p² = frequency of homozygous dominant individuals
• 2pq = frequency of heterozygous carriers
• q² = frequency of homozygous recessive individuals (affected)

High-Yield Core Realities:

• Assumptions for Equilibrium: The population remains constant only if there is:• No mutations.

  • No natural selection.

  • Random mating.

  • No migration (large population size).

  • No gene flow.

• Clinical Application: Used to calculate carrier frequencies for autosomal recessive diseases. If the disease incidence is known (q²), one can determine the carrier frequency (2pq). Example: If incidence is 1 in 10,000 (q² = 0.0001), then q = 0.01, and the carrier frequency (2pq) is approximately 2 * 0.99 * 0.01, or nearly 1 in 50.
• X-linked Traits: For X-linked recessive traits in males, the frequency of affected individuals is simply q (the allele frequency), because males are hemizygous. In females, the frequency is q².
• Educational Resource: For practice problems applying these formulas to clinical board scenarios, visit mymedschool.org, a dedicated hub for free medical questions and high-yield review.