Patterns of Inheritance

Genes exist in pairs within an organism, with one of each pair inherited from each parent.

The observable traits expressed by an organism are referred to as its phenotype and its underlying genetic makeup is called its genotype.

A Punnett square applies the rules of probability to predict the possible outcomes of a monohybrid cross and their expected frequencies.

With the inclusion of incomplete dominance, codominance, multiple alleles, and mutant alleles, the inheritance of traits is complex process.

A gene present on one of the sex chromosomes (X or Y in mammals) is a sex-linked trait because its expression depends on the sex of the individual. 

Inheriting two copies of mutated genes that are nonfunctional can have lethal consequences.