Single Gene Inheritance

• Single gene inheritance refers to an inherited characteristic that is controlled by a single gene, with either one or two alleles.
• Each gene resides at a specific position on a chromosome.
• An allele is a variant of a gene, which can cause different character traits, from physical features such as eye colour to various medical conditions.
• In sexually reproducing organisms, an individual inherits two copies (alleles) of each gene, one from each parent.
• One allele might be dominant over the other; in that case, the organism will display the trait associated with the dominant allele.
• If both alleles for a gene are the same, the organism is known as homozygous for that gene.
• If the two alleles for the gene are different, the organism is heterozygous.
• When both alleles are identical, they are called homozygous, whereas non-identical pairs are heterozygous.
• If both parents carry at least one recessive allele for a genetic quality, there is a potential for this trait to be expressed in their offspring.
• Single-gene disorders, like cystic fibrosis and sickle cell disease, are caused by the mutation of a single gene. The traits for these disorders can be inherited using the principles of dominant and recessive alleles.
• Gregor Mendel’s experiments on pea plants used single gene inheritance to demonstrate basic principles of genetics, such as dominance, recessiveness and segregation. These principles still underpin the study of genetics today.
• Punnett squares are used to predict the possible genetic outcomes for the offspring of two parents. This graphical method is a powerful tool for understanding single gene inheritance.
• Phenotype refers to the physical expression of a gene, while genotype refers to the actual pair of alleles an individual carries for a certain trait.
• In the context of single gene inheritance, these principles allow us to predict the genetic makeup (genotype) and physical traits (phenotype) of offspring.