Basic Definitions (Inheritance - Intermediate Part II)

Basic Definitions

Inheritance: Inheritance is the process of character transmission from individuals of one generation to the next. It is regulated by the genes present on chromosomes.

Genetics: The branch of biology concerned with the study of inheritance, or the transmission and expression of genetic information.

Character: Any heritable feature or characteristic of an organism is known as a character e.g. Height, Intelligence, blood group, and hair color.

Trait: A Variant of a character is called a trait e.g. black or brown hair color, and short or tall stature. These are characteristics that an organism displays. Also include the organism’s behavior (behavioral traits).

Gene: Gene is the unit of heredity. It is a segment of DNA that contains the information to make a functional protein.

Allele: Alleles are the alternative form of a specific gene. Alleles Control the same characteristics (e.g. hair color) but produce different effects (e.g black or red)

Back cross: Back cross refers to a cross of F 1 hybrids to individuals with genotypes of the parental generation or with its parents.

Test cross: A cross between a recessive individual and a dominant individual whose genotype is unknown (Homozygous or heterozygous) is known as a test cross.

Pure breeding: An individual with two identical alleles of a particular gene or an individual that when self-crossed produces progeny of its own type.

Hybrid: An individual that has two different alleles of a particular gene A progeny individual from any cross involving parents of different alleles.

Dominant Allele: An allele that determines the phenotype in the heterozygous condition. For example, if a plant is Tt and has a tall phenotype, the T (tall) allele is dominant over the t (dwarf) allele.

Recessive allele: A gene that is masked by the presence of a dominant gene is called recessive.

Reciprocal Crosses: A pair of crosses in which the traits of the two parents differ about gender. For example, one cross could be a red-eyed female fly and a white-eyed male fly, and the reciprocal cross would be a red-eyed male fly and a white-eyed female fly.