What are Alleles?

Alleles are different versions of a gene that can lead to variations in a particular characteristic, such as hair color or blood type. They are located at the same position on homologous chromosomes.

Dominant and Recessive Alleles

A dominant allele is expressed when present, masking the expression of a recessive allele. A recessive allele is only expressed when two copies are present, as it is masked by the dominant allele.

Mendelian Inheritance

Alleles follow the principles of Mendelian inheritance, where dominant and recessive traits are passed down from parents to offspring according to specific patterns.

Genotype and Phenotype

Genotype refers to the genetic makeup of an organism, while phenotype refers to the observable physical or biochemical characteristics resulting from the interaction of the genotype with the environment.

Genetic Crosses

Genetic crosses, such as Punnett squares, can be used to predict the outcomes of offspring based on the alleles inherited from the parents.

Genetic Disorders

Some genetic disorders are the result of inheriting certain combinations of alleles. For example, cystic fibrosis is caused by inheriting two copies of the recessive allele for the CFTR gene.