Single Gene Inheritance

DNA (Deoxyribonucleic acid) carries genetic information in cells. It’s composed of chromosomes, made up of a specific combination of genes.
Single gene inheritance means a trait is controlled by a solitary gene. This gene may have different versions known as alleles.
Each person has two alleles for each gene, one from their mother and one from their father.
Dominant alleles are expressed if present, meaning they can override the other version of the gene.
Recessive alleles are only expressed if two copies are present, meaning there’s no dominant allele present.
The two alleles together are known as the genotype of an individual.
The physical trait that is expressed, be it the dominant or recessive trait, is known as the phenotype.
When two of the same alleles are present (e.g., both dominant or both recessive), this is referred to as homozygous.
When there are two different alleles present (one dominant, one recessive), this is called heterozygous.
Single gene inheritance can be displayed using Punnett squares, which predict potential offspring genotypes and phenotypes from parental alleles.
Some traits might not follow the single gene inheritance pattern due to multiple allele inheritance or interaction of different genes. These traits are referred as polygenic traits.
Some common examples of single gene traits include widow’s peak, earlobe attachment, and the ability to roll the tongue.