Phenotypic Features

• Phenotypic features refer to the observable characteristics of an organism. These include physical traits like height, eye colour, and hair type, as well as physiological traits such as blood type or sickle cell trait.

• Phenotypic characteristics are determined by an individual’s genotype, the unique combination of genes inherited from both parents.

• An organism’s environment can also influence certain phenotypic traits. For example, exposure to sun can affect skin colour, and nutrition can influence height.

• Phenotypic variation among individuals in a population is due to different combinations of genes and different environmental influences.

• Characteristics are typically categorised as either continuous or discontinuous. Continuous variation shows a full range of intermediate forms, such as height in humans. Discontinuous variation does not show any intermediate forms, and individuals can be clearly categorised, such as blood groups in humans.

• Each characteristic may be influenced by one or many genes. For instance, eye colour is influenced by multiple genes, making it a polygenic trait. On the other hand, traits like blood group are determined by a single gene.

• Some traits are controlled by dominant and recessive alleles. A dominant allele will always express its trait, even if only one copy is present. However, a recessive allele will only express its trait when two copies are present (one from each parent).

• Some phenotypic traits can be used to study inheritance patterns in families, known as Mendelian patterns. These include clearly defined traits like attached or detached earlobes, hitchhiker’s thumb, or tongue rolling ability.

• Phenotype is not always a direct predictor of genotype as certain traits can be influenced by more than one gene (polygenic traits) or by environmental conditions.