Post on 21-May-2015
MENDEL’S EXPERIMENT ON HYBRIDIZATION&
MONOHYBRID CROSS
ByDr. ICHHA PURAKUNIVERSITY PROFESSOR IN BOTANYRANCHI WOMEN’S COLLEGE,RANCHI
Website : www,dripurak.com
04/12/23MENDEL'S EXPERIMENT1
GREGOR JOHANN MENDEL ( 1822-1884 )
04/12/23MENDEL'S EXPERIMENT2
Brief Introduction : Gregor Johann Mendel
Hybridization
Reasons for selecting sweet pea as Experimental
Plant
Alternative forms in sweet pea
Steps in hybridization experiment
Monohybrid cross
Results of the Experiment
Genetic Expression of Monohybrid cross
Mendel’s conclusions
Law of Dominance and Law of Segregation
Brief INTRODUCTION
GREGOR JOHANN MENDEL ( 1822-1884)
Born on July 22,1822 at Austria in a Farmer’s Family
School Level education at Austria
In 1853 joined as Priest in Monastery at Brunn
Continued Higher Education simultaneously
In 1854 was appointed as science teacher
He lived in a house in the premises of church
He used to spare free time in gardening
He became interested to know about transmission
of
characters over generations04/12/23MENDEL'S EXPERIMENT
3
04/12/23MENDEL'S EXPERIMENT4
He started his experiment of hybridization on sweet
pea in 1857 ,continued till 1865 (8 years )
In 1865, he presented his paper before Natural History
Society, Brunn
In 1866 the paper was published in the proceedings of the
society
In 1900 Mendel’s work was rediscovered by Hugo de Vries
(Holland), Carl Correns (Germany) and E V Tschermak
(Austria)
These three scientist named the laws of inheritance as
Mendel’s laws of inheritance in honour of Mendel.
Since then Mendel is known as “Father of Genetics”
04/12/23MENDEL'S EXPERIMENT5
HYBRIZATION IN PLANTS
Hybridization is frequently employed in agriculture, to
make stronger, healthier plants with desirable
characteristics.
In plants hybridization is done by artificial cross pollination
For example, a cross between parent 1(Tall), with the
genetic makeup (genotype) TT, and parent 2( Dwarf), with
tt, produces progeny with the genetic makeup Tt, which is
a hybrid (the first filial generation or F1)
Hybridization was the basis of Mendel’s historic
experiments with garden peas. Inheritance studies require
crossing plants with contrasting or alternative traits
04/12/23MENDEL'S EXPERIMENT6
REASONS FOR SELECTING SWEET PEA (Pisum sativum ) AS EXPERIMENTAL PLANT
04/12/23MENDEL'S EXPERIMENT7
Pisum sativum (Sweet Pea ) is a self pollinated plant
It is suitable for artificial cross pollination
It bears large flowers,emasculation and pollination easy
It is annual,results are obtained yearly
Pure lines are easily available as it is naturally self
pollinated
It shows several varieties showing contrasting forms of
characters
04/12/23MENDEL'S EXPERIMENT8
S N Trait Alternative Forms
Dominant Recessive
1 Seed shape Round Wrinkled
2 Seed colour Yellow Green
3 Flower Colour Purple ( Red) White
4 Pod shape Inflated ( Full ) Constricted
5 Pod colour Green Yellow
6 Flower position Axial Terminal
7 Stem Height Tall (2m) Dwarf (0.5m)
Seed coat colour Grey White
ALTERNATIVE FORMS IN SWEET PEA
04/12/23MENDEL'S EXPERIMENT9
04/12/23MENDEL'S EXPERIMENT10
04/12/23MENDEL'S EXPERIMENT11
STEPS IN HYBRIDIZATION EXPERIMENT• SELECTION OF PURE BREEDING PARENTS
• Emasculation
• Bagging
• Seed setting
• Collection of seeds
• Raising of F1 generation plants
• F1 plants self pollinated
• Seed setting of F1 plants
• Collection of seeds from F1 plants
• Raising F2 generation plants
• Raising F3Plants →F4 plants→F5 plants →→F7 plants.
04/12/23MENDEL'S EXPERIMENT12
MONOHYBRID CROSS
Monohybrid cross is a cross when only one trait and its two
alternative forms are considered during hybridization
experiment 1.Purple flowered male plant is crossed with white flowered female plant 2 . Tall male plant is crossed with dwarf female plant
Steps in Monohybrid cross: Trait : Height of plant : Tall Vs Dwarf
Testing of parental plants for purity
Consideration of a plant as Male parent whose pollen are
used
Consideration of a plant as female parent whose stigma is
used
From flowers of female plants anthers are removed before
anthesis- Emasculation
04/12/23MENDEL'S EXPERIMENT13
Emasculated flowers were covered in porous paper bags to avoid
undesired cross pollination
Hybridization or artificial cross pollination was done by dusting
pollen
from flowers of male plants on stigma of flowers on female plant
Fertilized flowers were left on plants to set seeds
Seeds were collected separately from each plant
Seeds were sown next year to raise F1 plants
F1 plants were left to self pollinate
Seeds were collected separately from each plant of F1 generation
Seeds were sown to raise F2 plants
F2 generation plants were left to self pollinate
Seeds of F2 plants were collected
F3 generation plants were raised
F4 ----------→ F5 ----------→ F6 ----------→ F7 plants were raised
04/12/23MENDEL'S EXPERIMENT14
Results of the experiment ( Monohybrid Cross between
Tall male plant and female dwarf plant ) and Vice Versa
• F1 Generation – All plants were tall (Dwarfness disappeared)
• F 2 Generation – Tall and Dwarf plants both appeared in ratio approximately
3:1
• F3 Generation – Of the tall plants of F2 some plants gave tall and some
segregated again into Tall and Dwarf in 3:1 ratio and dwarf plant gave only
dwarf plant
• F4 Generation – Some tall plants of F3 generation gave Tall only and some
again
segregated in 3:1 ratioSuch Monohybrid crosses were made for all the seven traits and
their alternative forms and in all cases the dominant form
appeared in F1 generation, In F2 both Dominant and Recessive
appeared in 3:1 ratio.
04/12/23MENDEL'S EXPERIMENT15
Genetic Expression and Analysis of Results of Monohybrid cross___________________________________________________________Parents Tall Male (TT) X Dwarf Female (tt)_____________________________________________________________________________Parental gametes T t____________________________________________________________________________Hybridisation Tt ( Zygote →Seed) F1 Plants (All Tall )_____________________________________________________________________________Hybrid Gametes (F1) Male → T(1) and t (2) Female→ T(3) and t(4)____________________________________________________________________________Self Pollination TT (1,3) Tt (1,4) Tt(2,3) tt (2,4) F2 Progeny ( Tall : Dwarf,3:1) Tall Tall Tall Dwarf -------------------------------------------------------------------------------------------------------- ↕ ↕ ↕ ↕ TT TT Tt Tt tt TT Tt Tt tt tt F3 Progeny ( Tall : Dwarf, 7:3 ) Tall Tall Dwarf Tall Dwarf Dwarf _____________________________________________________________________________
04/12/23MENDEL'S EXPERIMENT16
Genetic Expression of Monohybrid cross (Punnet’s Square )
Parents---- TT Tall (Male ) X tt Dwarf ( Female) Parental gametes ---- T t
Hybrid ------- Tt F1 (All Tall)
F1 gametes Female
Male T t
T TT Tt
t Tt tt
Phenotypic Ratio----- 3:1
Genotypic Ratio ------ 1:2:1
F2 Generation
04/12/23MENDEL'S EXPERIMENT17
MENDEL’S CONCLUSION ON THE BASIS OF MONOHYBRID
CROSS Something is transferred from one generation to other ,which
carries information for expression of the trait.
This something is particulate in nature .
Mendel called this particulate thing as Factor or Determiner
Mendelian factor is now termed as gene
Genes are present in linear fashion on specific loci(position)on
homologous chromosomes in pairs
Each gene exist in two forms or alleles and govern expression
of
alternative phenotype (Allelomorphs ) such as Tall and DwarfOn the basis of result of F1 generation of Monohybrid
crosses for all the seven traits Mendel proposed
04/12/23MENDEL'S EXPERIMENT18
Law of Dominance states that in a cross pure for two
contrasting /Alternative forms of a trait , the one which
expressed itself in F1 generation is dominant and is able to
suppress the expression of other (Recessive ) form.
On the basis of result of F2 generation obtained in monohybrid
cross Mendel proposed
Law of Segregation (Law of purity of gametes/Law of
Unit characters ) states that when a pair of alleles ( Alternative
forms of a gene ) are brought together in a hybrid,they donot mix
up or blend but remain associated with each other and separate
or segregate from each other in next generation when hybrid
forms gametes.
04/12/23MENDEL'S EXPERIMENT19
MONOHYBRID CROSS : TALL PLANT Vs DWARF PLANT
04/12/23MENDEL'S EXPERIMENT20
04/12/23MENDEL'S EXPERIMENT21
Mendel’s Monohybrid Cross ( Round seed Vs wrinkled seed ) reciprocal crosses on two sides 04/12/2322
04/12/23MENDEL'S EXPERIMENT23
04/12/23MENDEL'S EXPERIMENT24
Trait Parental cross
F1
Phenotype
F2 Phenotypes Total F2
Ratio Dominant
Recessive
Seed Shape
Round x Wrinkled
Round 5474 Round
1850 Wrinkled
7324 2.96:1
Cotyledon colour
YellowxGreen
Yellow 6022 Yellow
2001 Green
8023 3.01:1
Seed Coat Colour
Grey x White Grey 705 Grey 224 White
929 3.15:1
Pod Colour Green x Yellow
Green 428 Green
152 Yellow
580 2.82:1
Pod shape Inflated x Constricted
Inflated 882 Inflated
299 Constricted
1181 2.95:1
Position of flower
Axial x Terminal
Axial 651 Axial 207 Terminal
858 3.14:1
Length of stem
Tall x Dwarf Tall 787 Tall 277 Dwarf
1064 2.84:1
Colour of flower
Purple x White
Purple
SUMMARY OF F2 DATA OBTAINED By MENDEL IN PEA FROM DIFFERENT MONOHYBRID CROSSES
04/12/23MENDEL'S EXPERIMENT25
THANK YOU