Genetics formulas are mathematical expressions used to predict how traits are inherited from one generation to another. These formulas help in calculating genotype frequency, phenotype ratio, and allele distribution in populations.

1. Hardy-Weinberg Equation

Formula: p² + 2pq + q² = 1

This formula is used to calculate genetic variation in a population under equilibrium.

• p² = Homozygous dominant
• 2pq = Heterozygous
• q² = Homozygous recessive

Example:

If q² = 0.04, then q = 0.2 and p = 0.8 Genotype frequency:

• p² = 0.64
• 2pq = 0.32
• q² = 0.04

2. Mendelian Genetics Formula

Mendelian genetics uses probability rules to determine trait inheritance.

Law of Segregation Formula

Each parent contributes one allele:

Probability = 1/2

Law of Independent Assortment

Traits are inherited independently:

Probability = (1/2)ⁿ

3. Probability Formula in Genetics

Formula: P(A and B) = P(A) × P(B)

Example:

Probability of two independent traits:

= 1/2 × 1/2 = 1/4

4. Punnett Square Formula

Punnett square helps calculate genotype combinations:

Monohybrid cross ratio:

3:1 (Phenotype)

Genotype ratio:

1:2:1

Solved Examples

Example 1:

If frequency of recessive allele is 0.3, find dominant allele.

p = 1 - q = 1 - 0.3 = 0.7

Example 2:

Find genotype frequency using Hardy-Weinberg:

p = 0.6, q = 0.4

• p² = 0.36
• 2pq = 0.48
• q² = 0.16

Frequently Asked Questions (FAQs)

What is the most important genetics formula?

The Hardy-Weinberg equation is the most important formula used to study population genetics.

Why are genetics formulas important?

They help predict inheritance patterns and genetic variation.

What is p and q in genetics?

p represents dominant allele frequency and q represents recessive allele frequency.