Genetics

Genetics

»   Transmission of character from one generation to next generation is called heredity.
»   The process of transfer of hereditary character from generation to generation is called genetics.
»   The name genetics was first coined by W. Wattson in 1905.
»   Johannes was first used the name gene in 1909.
»   Gregar Johan Mendal was the first who gave the idea of heredity based on his experiment in 1822-1884. He is also known as father of genetics.
»   Mendal chosen pea plant for his experiment.
»   Mendal made a cross between two pure plant having contrasting character for single trait called monohybrid cross i.e. tall and dwarf plant for height.

Dihybrid cross

Mendal made a cross between two pure plant having in two pair of contracting character i.e. colour and shape of seed called dihybrid cross.
He made a cross between plant having round seed with yellow colour and wrinkled seed with green colour.

Law of paired unit

Mendal proposed that when two dissimilar unit factors are present in an individual only one is able to express. One that expresses it setf is dominant unit factor while other which fail to express is recessive unit factor.

Law of dominance

Offspring of cross breed parent only show dominant characters in First generation.

Law of segregation

In Second generation both the character which is governe by gene is separated.

Law of independent assortment

During dihybrid and cross two or three pair of characters are taken. These characters segregate separately without depending on other in Second generation.

Term related to genetics

Linkage : Linkage is an exception of Mendel law. When two different gene are present on the same chromosome they express them self together instead of independently. This phenomenon is known as Linkage. The word linkage first coined by Morgan (1910).

Mutation: A sudden change in the gene which is heritable from one gene to other. The term Mutation was first coined by Hugo De Vries.

Variation : When characters are, transmitted, from one generation to next generation there is some change. Change in characters by recombination of gene in offspring takes place they looks different from their parents. This phenomenon is known as Variation.

Chromosomal aberrations : Any change in chromosomal structure is known as Chromosomal aberrations.

cloning: It is a process of producing many identical organism from a single cell having same genetic character as his mother. Ex : Sheep Dolly was produced from single cell.

Totipotency: It is the potential ability of a plant cell to grow in a complete plant.

Pluriopotency: It is the potential ability of a cell to develop into any kinds of the cell of animal body.

Genetically modified organism (GMO) : Manipulation of gene by cutting or joining the segment of DNA to get desired varieties of organism is called genetically modified organism. This is also known as genetic engineering.

Autosomes: Chromosomes found in cell which are responsible for characters other than sex are called autosomes.

Sex chromosome: The pair of chromosome which determine the sex of organism is called sex chromosome.

Human have 23 pair of chromosomes in which 22 pair are autosomes and one pair is sex chromosome.

Genome : All gene present in a haploid cell is called genome.

Plasmagen : Gene are found in organelles found in cytoplasm called plasmagen.

Cistron : Functional unit of gene is called cistron.

Muton : Unit of gene responsible for mutation.

Recon: Unit of gene take part in recombination.