Laws of Heredity

7/24/2019 Laws of Heredity

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Laws ofHeredity


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Mendels Laws of Heredity

Gregor John Mendel is calledthe father of Modern Genetics.

His experiments revealed someinteresting facts aboutinheritance of genes. The

inheritance of parentalcharacters by the ospring is

called heredity.


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When type of character or traitwas considered he named it asmonohybrid cross and for

two types of characters it wascalled dihybrid cross. Whenmore than two types of

characters were considered forexperimenting it was calledpolyhybrid cross.


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The progeny obtained from crossing

two pure individuals is called thehybrid and the process is calledhybridization. The parental

generation is denoted as and theprogeny of hybrids obtained fromthem are denoted as F1

generation and when !" is selffertili#ed the resulting progeny iscalled F2 generation.


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$ubse%uent generations fromself fertili#ations are called F3,F, F! and so on. When !"

hybrid is crossed with one ofthe parents the operation iscalled bac" crossingand if !"

hybrid is crossed with arecessive parent it is called atest cross.


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!rom his experiments Mendelpropounded following principles

&nown as Mendel's (aws of Heredity)

Law of #ominance$+ut of the two

contrasting characters that wereconsidered in the parental generationonly one appeared in the !"generation. This character that

remains apparent in !" hybrid istermed as dominant character and theother character as recessive character.


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Law of %egregation$This isalso &nown as law of purity and

according to this law during thegamete formation, from a pairof contrasting characters only

one can be represented in asingle gamete by its germinal

unit.


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Law of &ndependent

'ssortment$-ccording to this law,when two or more pairs of

characters segregate

simultaneously, the distribution ofany one of them is independent ofthe distribution of the other. The

relation of each pair of dierentcharacters in hybrid union isindependent of their dierence in

the original parental stoc&.


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&ncomplete #ominance$The ruleof dominance and recessiveness

does not hold good in all the cases.When a character is chosen in aparental generation and neither

gene from any of the parents mayshow dominance, therefore notappear in !" generation, butinstead an intermediate form of thisparental character is seen. Hereboth the genes express themselvespartially so the phenomenon is

called ncomplete /ominance and


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(elate Mendel)s Laws

of &nheritance with*enes + theirtransmission

Laws of Heredity

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