Mendel,s law of segregation( monohybrid cross)

1. Azhar Zeb M.Sc Zoology Contact 009203469447715/[email protected]
Mendel,s law of Mendel,s law of
segregation( monohybrid cross)segregation( monohybrid cross)

STATEMENT; when a pair of contrasting traits are STATEMENT; when a pair of contrasting traits are
brought together in a cross, members of the allelic pair brought together in a cross, members of the allelic pair
remain together in the first generation(F1) and remain together in the first generation(F1) and
segregates in the next generation(F2).segregates in the next generation(F2).
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OrOr
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When two different alleles for a trait are brought together When two different alleles for a trait are brought together
in an individual they stay together but at the time of in an individual they stay together but at the time of
gamete formation the two allels separates/segregates gamete formation the two allels separates/segregates
from one another so each gamete has one allele not from one another so each gamete has one allele not
both.both.

2. Azhar Zeb M.Sc Zoology Contact 009203469447715/[email protected]

EXPLAINATION:EXPLAINATION:
Mendel crossed true breeding tall (TT) pea Mendel crossed true breeding tall (TT) pea
plant with true breeding dwarf (tt) pant.plant with true breeding dwarf (tt) pant.
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This parental generation was called as P1 This parental generation was called as P1
or parental generation.or parental generation.
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All offspring's obtained were uniformly tall.All offspring's obtained were uniformly tall.
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This generation was called as F1 or first This generation was called as F1 or first
filial generation.filial generation.

3. Azhar Zeb M.Sc Zoology Contact 009203469447715/[email protected]

The trait which appeared in F1 was called The trait which appeared in F1 was called
dominant while the trait which disappeared dominant while the trait which disappeared
was called as recessive.was called as recessive.
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The F1 plants were self fertilized and The F1 plants were self fertilized and
offsprings produced were called as F2 offsprings produced were called as F2
generation.generation.
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Three types of plants were present in F2 Three types of plants were present in F2
i.e. pure tall, hybrid tall and dwarf.i.e. pure tall, hybrid tall and dwarf.

4. Azhar Zeb M.Sc Zoology Contact 009203469447715/[email protected]
Graphical representationGraphical representation

The cross b/w true breeding tall pea plant and pure The cross b/w true breeding tall pea plant and pure
breeding dwarf pea plant can be graphically shown as breeding dwarf pea plant can be graphically shown as
follows.follows.
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P1-------------- Tall P1-------------- Tall ×× Dwarf Dwarf
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F1-------------- All TallF1-------------- All Tall
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If tall plants are represented by TT and dwarf plant by tt If tall plants are represented by TT and dwarf plant by tt
then the above cross can be shown as.then the above cross can be shown as.
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P1-------------- TT P1-------------- TT × × tt tt
xx
F1----------------------F1----------------------

TT tt
Tt

5. P2 --------------- x P2 --------------- x
xx
F2-------------- F2--------------
Tt Tt
Tt Tt
TTTtTttt
Phenotypic ratio Tall : DwarfPhenotypic ratio Tall : Dwarf
3 : 13 : 1
Genotypic ratio pure tall : hybrid tall : dwarf.Genotypic ratio pure tall : hybrid tall : dwarf.
1 : 2 :11 : 2 :1

6. Azhar Zeb M.Sc Zoology Contact 009203469447715/[email protected]
6copyright cmassengale

7. Azhar Zeb M.Sc Zoology Contact 009203469447715/[email protected]

Phenotyphic ratio Tall : DwarfPhenotyphic ratio Tall : Dwarf
3 : 13 : 1
Genotyphic ratio pure tall : hybrid tall : dwarf.Genotyphic ratio pure tall : hybrid tall : dwarf.
1 : 2 :11 : 2 :1