Genetics: Study of heredity and variation.
Heredity: Inheritance of characters transmitted from parents to offsprings.
Variation: Degree by which progeny differ from their parents.
Father of genetics- Gregor Johann Mendel.
He conducted experiments in garden pea(Pisum sativam)
He conducted experiments in garden pea(Pisum sativam)
Reasons for selecting garden pea,
1.Bisexual flower.
2.Self and cross pollination takes place.
3.Contrasting pairs of characters.
4.Short life span.
1.Bisexual flower.
2.Self and cross pollination takes place.
3.Contrasting pairs of characters.
4.Short life span.
There is a particular gene for a particular character.
For indicating a gene ,there are two alleles.
For indicating a gene ,there are two alleles.
Experiment
1.True breeding
(Producing same character from same plants by producing them for 3-4 generation,made them pure for that specific character)
By self pollination,he created two pure breeding Tall and a pure breeding dwarf.
A character has two forms a dominant and a recessive form.
For example Height has two forms one is Tall and the other is dwarf.
2.A pure breeding Tall is crossed with a pure breeding dwarf.
At the time of gamete formation,the two factors separate or segregate.
The next generation is known as F1 generation or first filial generation.
In F1 generation, Dominant character T is expressed.
And T is completely dominant over t -- complete dominance.
Thus it expresses tallness.
This observable character is called phenotype.The genetic constitution is called genotype.
(Producing same character from same plants by producing them for 3-4 generation,made them pure for that specific character)
By self pollination,he created two pure breeding Tall and a pure breeding dwarf.
A character has two forms a dominant and a recessive form.
For example Height has two forms one is Tall and the other is dwarf.
2.A pure breeding Tall is crossed with a pure breeding dwarf.
At the time of gamete formation,the two factors separate or segregate.
The next generation is known as F1 generation or first filial generation.
In F1 generation, Dominant character T is expressed.
And T is completely dominant over t -- complete dominance.
Thus it expresses tallness.
This observable character is called phenotype.The genetic constitution is called genotype.
3.Then the F1 generation is self polinated.Tt*Tt
At gamete formation,both alleles segregate,
TT Tt Tt tt are formed
Phenotype - 3 tall and 1 short is formed.
Genotype - 3genotype TT Tt tt
Phenotypic ratio-3:1
Genotypic ratio-1:2:1
Monohybrid cross-The character of one is crossed.
Phenotypic ratio-3:1
Genotypic ratio-1:2:1
Monohybrid cross-The character of one is crossed.
Reginald C Punnett brought a square called Punnett square or check board for easily finding the phenotype and genotype.
No comments:
Post a Comment