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 proves 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 polyhydric
cross.
Allelic pair: A pair of genes
controlling a pair of contrasting characters.
Allele: One member of a pair
of series of genes that occupy specific position on a specific chromosome is
called allele/ allele morph.
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 alternating characters is called hybridization.
F1
generation:
The generation obtained by crossing two parental stokes.
F2
generation:
The generation obtained by crossing two parental stokes of F1
generation.
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 arises due
to changes in the germ cells is called blastogenic variation.
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