Mendel's law of segregation describes how contrasting traits segregate in a monohybrid cross over two generations. In the F1 generation, the traits remain together, but in the F2 generation they segregate such that each gamete receives one of the two alleles. Mendel demonstrated this by crossing true-breeding tall and dwarf pea plants. The F1 generation was uniformly tall, but the F2 generation showed a 3:1 ratio of tall to dwarf plants, with genotypic ratios of 1:2:1 for pure tall:hybrid tall:dwarf.

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

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

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

4. Graphical representation
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The cross b/w true breeding tall pea plant and pure
breeding dwarf pea plant can be graphically shown as
follows.
P1-------------- Tall × Dwarf
F1-------------All Tall
If tall plants are represented by TT and dwarf plant by tt
then the above cross can be shown as.
P1-------------- TT
× tt
T T x t t
F1----------------------
Tt
Azhar Zeb M.Sc Zoology Contact 009203469447715/izhaar

5. P2 ---------------
F2-------------Phenotypic ratio
x
Tt
Tt
T t x T t
TT
Tall
Tt
Tt
: Dwarf
3 : 1
Genotypic ratio pure tall : hybrid tall : dwarf.
1 :
2
:1
tt

6. Azhar Zeb M.Sc Zoology Contact 009203469447715/izhaar
copyright cmassengale
6

7. 
Phenotyphic ratio
Tall : Dwarf
3 : 1
Genotyphic ratio pure tall : hybrid tall : dwarf.
1 :
2
:1
Azhar Zeb M.Sc Zoology Contact 009203469447715/izhaar