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Genetics word first used by => W. Watson
(in 1905).
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Transmission of character from
one generation to next generation is called
Heredity.
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The process of transfer of hereditary character from generation to
generation called as Genetics.
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The characteristics which transmit from generation to generation is
transported by Gene.
Gene:
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Gene word first coined by =>
W. Johannsen (in 1909).
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It is a unit of hereditary material located on
chromosome.
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Gene itself or with other gene determine character of
organism.
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Gene exist in number of alternative forms termed as
alleles.
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Gene occasionally undergo for radial changes called as
Mutation.
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The modern concept of perception about the gene was given by
=> Benjer (in 1956).
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Functional unit of gene =>
Cistron
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Unit of gene responsible for mutation =>
Muton
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Unit of gene take a part in recombination =>
Recon
- In Human 35000 gene are present.
|
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Gregor Johann Mendel said that hereditary character is transfer by
gene.
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Hence Gregor Johann Mendel is known as
Father of Genetics.
Mendel's Experiment:
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Mendel chooses 7 pair of pea plant species for his experiment.
Characters
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Dominant characters
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Recessive characters
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Shape of the seed.
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Spherical smooth seed.
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Wrinkled seed.
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Color of the cotyledon.
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Yellow |
Green |
Color of flower.
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Red |
White |
Shape of the fruit.
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Smooth |
Shrinked
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Color of the fruit.
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Green |
Yellow |
Position of the flower.
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Tall |
Farthest
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Length or Height of the plant.
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Tall |
Dwarf |
Mono-hybrid Cross:
Mendel made cross between 2 pure plant having contracting character for
single trait called Mono-hybrid cross (i.e. Tall & Dwarf plant for
height)
Phenotype ratio => 3 : 1
Genotype ratio => 1 : 2 : 1
Di-hybrid Cross:
Mendel made cross between 2 pure plant having in 2 pair of
contracting character i.e. color & shape of seed called Di-hybrid
cross. (i.e. Plant having round seed with yellow color & wrinkle
seed with green color.)
Phenotype ratio => 9 : 3 : 3 : 1
Genotype ratio => 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1
Mendel's Law of Heredity:
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On the basis of mono-hybrid and Di-hybrid cross Mendel proposed law
of heredity.
1.
Mendel's First Law: (Law of dominance)
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According to it when two dissimilar unit factors are present in an
individual only one is able to express.
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One that express itself is dominant character while which
fail to express is recessive character.
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In the first generation only the
dominant character is visible, while the
recessive character is hidden and it appears in the next
generation.
2.
Mendel's Second Law: (Law of segregation)
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According to this law during the gametes formation both the
character which governed by gene is segregated and out of these
factors only one factor is reached in the gamete.
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Both factors never come at a time in the gamete.
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This law is also called the
Law of purity of Gametes.
3.
Mendel's Third Law: (Law of Independent Assortment)
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According to this law various pairs of the factors which
exist in organism are independent to each other.
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Thus organism of new appearance may born.
Terms Related to Genetics:
- Phenotype:
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The characteristics of the organism which are directly &
visibly appreciable is called Phenotype.