The Foundations of Genetic Prediction

Mendel’s Laws

Gregor Mendel's experiments with pea plants established the fundamental laws of inheritance. The Law of Segregation states that allele pairs separate during gamete formation, so each sperm or egg receives only one allele for each trait.

The Law of Independent Assortment describes how alleles for different traits are inherited independently of one another (assuming they’re on different chromosomes). This allows for a huge variety of possible combinations in offspring.

Segregation: 2n → n, where n = # of alleles per trait.

Dominance and Recessiveness

In a heterozygous genotype (e.g., Aa), one allele may mask the expression of another – this is dominance. The dominant allele’s phenotype is expressed.

The recessive allele, only present in its homozygous form (aa), remains hidden and its associated trait is only visible when two copies are inherited.

P(dominant) > P(recessive) when heterozygous

Punnett Squares

Punnett squares are tools used to predict the genotypes and phenotypes of offspring based on the parental genotypes. They visually represent all possible allele combinations.

By constructing a Punnett square, we can calculate the probability of specific traits appearing in the next generation – probabilities, not certainties.

Punnett Square: A grid representing allele combinations for predicted offspring.

Beyond Simple Inheritance

While Mendelian genetics explains many traits, inheritance isn't always simple. Complex inheritance patterns involving multiple genes and environmental factors exist.

Epistasis describes interactions between alleles at different loci influencing a single trait. Polygenic inheritance involves multiple genes contributing to one continuous phenotype (e.g., height).

Complex Inheritance: Multiple gene interaction + Environmental Influence

Frequently asked questions

Try it live

Everything above runs in your browser — open Michaelis-Menten Kinetics and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.