Definitions (Heredity)

HEREDITY

Heredity: The process, by which living organism transmits parental characteristics to their offspring, is called heredity or inheritance.

Hereditary characters: Those characters which are transferred from parents to their offspring.

Genetics: The branch of biological science which deals with the nature and behavior of genes.

Hybrid: The organism produced after cross fertilization between two genetically different organisms.

Dominant characters: Those characters which express themselves by covering the other characters are called dominant characters.

Recessive characters: Those characters in a cross which are unable to express themselves in successive generation when there is presence of dominant characters are called recessive characters.

Phenotype: The external appearance of an organism is known as phenotype.

Genotype: The genetic constitution of an organism is called genotype.

Monohybrid cross: The cross involving only one pair of contrasting character is known as monohybrid cross.

Dihybrid cross: The cross involving two pair of contrasting character is known as dihybrid cross.

Variation: The structural differences that provides individuality to each member of species.

Mutation/Discontinuous variations: The sudden chromosomal change in genetic makeup of an organism is called mutation or discontinuous variation.

DNA : Double stranded macromolecule which is commonly found in chromosome.

RNA: A single stranded helically coiled macromolecule which is commonly found in cytoplasm and nucleus.

Polyhybrid cross: The cross involving more than a pair of contrasting characters is called polyhybrid cross.

Allelic pair: A pair of genes controlling a pair of contrasting characters.

Allele: One member of a pair or series of genes that occupy specific position on a specific chromosome is called allele or allelomorph.

Homozygous: When both alleles of a particular gene are identical it is called homozygous.

Heterozygous: When two allele of gene are not identical then they are said to be heterozygous.

Acquired characters: Some characters which are not inherited or transmitted from ancestors but acquired during life time is called acquired characters.

Hybridization: The process of crossing between two organisms having contrasting characters is called hybridization.

F₁ generation: The generation obtained by crossing two parental stocks.

F₂ generation: The generation obtained by self-crossing (selfing) the F₁ hybrids.

Continuous variation: The variation that occurs gradually is called continuous variation.

Monohybrid ratio: The ratio which is obtained in the F₂ generation when monohybrid cross is made.

Di hybrid Ratio: The ratio which is obtained in the F₂ generation when dihybrid cross is made.

Somatogenic variation: Variations that are acquired by an organism due to the influence of environment.

Blastogenic variation: Variations that arise due to changes in the germ cells are called blastogenic variation.