mapping of genes
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Whereas mother and father contribute
equal quantity of genes
goes to offspring from parents
nn
2n
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Augustinian priest and scientist
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Tall/dwarf
Purple/White
Round/Wrinkled
Yellow/Green
Green/Yellow
Full/ConstrictedAxial/Terminal
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Producing offspring by crossing these traits
MENDELS FIRST EXPERIMENTmade several crosses ofpea plant involving only one pair of character(tr
For eg. Red f lower White f lower
only one pair at a time
First parents for crossing
P1 GENERATION
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MENDELS TERMINOLOGIES
Character which masks or hides its partner
dominant recessive
dominant
In the next generation allflowers were purple
recessiveCharacter not exhibited inthe next generation
similarly
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Some factors
Which were always present in pairs
For eg. Tall (T T)/ dwarf(tt)
Yellow (YY)/Green (y
But, today we know these factors are nothing but
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MENDELS
SYMBOLS
CAPITAL LETTERS
SMALL LETTERS
Genes
always in
pairs
RED FLOWER WHITE FLOWER
During the formation of gametes
In P1 generation
Pair factors or genes separate or segregate
RR r r
F
1
RR rr
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RR rr
Pure Red Pure White
R R r r
Rr Rr Rr Rr
P1 Generation
F1 generation
(parental generation in a
breeding experiment)
(first-generation
offspring in a breeding
experiment)
(1st filial generation)
RED RED RED RED
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Appearance of any detectable characteristics of an individual PHENOTYPE
Genetic composition of an i ndividual GENOTYPE
P1 coloured plants F1 coloured plantsAppearance
Geneticcomposition
RED RED
RR Rr
Phenotype same
Genotype different
BLUE
Bb
Gametes R R R r
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RR Rr
rrRrr
R
R rF2 generation
(2nd filial generation)
(second- generation offspring
in a breeding experiment)
RED
RED RED
WHITE
What will happen if F1 PLANTS are self crossed ?
RED FLOWER 1 RED FLOWER 2
F1 PLANTSP2 GenerationRr Rr
R r rRGAMETES
Punnett square or chequerboarddia ram
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R r
RrR
rRr
RED
RED
RED
rr
WHITE
PHENOTYPERED 3
WHITE 1
GENOTYPERR 1
Rr 2
rr 1
RR
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PHENOTYPIC RATIOGENOTYPIC RATIO
RED FLOWERS
WHITE FLOWERS
929
705
224
3:1 1:2:1
2 types of F2 PLANTS
3 types o f F2 PLANTS
Rr rr
Homozygous HomozygousHeterozygous
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What will happen if a cross is made using two traits at a time?
Seed shape Seed colour
MENDEL took
Pea plants
Round,yellow seeds
two
Wrinkled ,green seeds
Two pair of contrasting characters
MENDELS DIHYBRID CROSS
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Pea plant with Yellow& rounded seeds
Pea plant with Green& wrinkled seeds
P1 Generation
F1 generation
RY RY ry ry
RrY
y
RrY
yRrY
y
Gametes
RRYY rry y
RrY
y
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RrY
y
RYryrYRy
P1 GAMETES
Parental combinations
P1 GAMETES
Parental combinatio
SELF
POLLINATION
to produce
GAMETES
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RY
RYRrYyRound
yellow
ry
rY
Ry
ryrYRy
RryyRoundgreen
rrYyWrinkled
yellow
RryyRound
green
RrYYRound
yellow
RRYyRound
yellow
RrYyRoundyellow
RrYyRoundyellow
RrYyRound
yellow
RRYyRoundyellow
rrYyWrinkled
yellow
RrYYRoundyellow
rrYYWrinkled
yellow
RRYYRound
yellow
RRyyRoundgreen
rryyWrinkled
green
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Phenotype - the physical feature resulting from a
genotype(e.g. Round ,yellow, Wrinkledgreen)
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RY
RYRrYyRound
yellow
ry
rY
Ry
ryrYRy
RRYYRound
yellow
RrYYRound
yellow
RRYyRound
yellow
RrYyRoundyellow
RrYyRoundyellow
RrYyRound
yellow
RRYyRoundyellow
RrYYRoundyellow
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S.N
.
PHENOTYPE NO. OF SQUARES IN
CHEQUERBOARD
PHENOTY
PIC RATIO
1 Round yellow 9 out of 16 9
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RY
RY
ry
rY
Ry
ryrYRy
rrYyWrinkled
yellow
rrYYWrinkled
yellow
rrYyWrinkled
yellow
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S.N
.
PHENOTYPE NO. OF SQUARES IN
CHEQUERBOARD
PHENOTY
PIC RATIO
1 Round yellow 9 out of 16 9
2 Wrinkled Yellow 3 out of 16 3
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RY
RY
ry
rY
Ry
ryrYRy
RryyRoundgreen
RryyRound
green
RRyyRoundgreen
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S.N
.
PHENOTYPE NO. OF SQUARES IN
CHEQUERBOARD
PHENOTY
PIC RATIO
1 Round yellow 9 out of 16 9
2 Wrinkled Yellow 3 out of 16 3
3 Round Green 3 out of 16 3
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RY
RY
ry
rY
Ry
ryrYRy
rryyWrinkled
green
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THUS THE PHENOTYPIC RATIO IS APPROXIMATELY 9: 3 :3: 1
Phenotype - the physical feature resulting from a
genotype(e.g. Round ,yellow, Wrinkledgreen)
S.N
.
PHENOTYPE NO. OF SQUARES IN
CHEQUERBOARD
PHENOTY
PIC RATIO
1 Round yellow 9 out of 16 9
2 Wrinkled Yellow 3 out of 16 3
3 Round Green 3 out of 16 3
4 Wrinkled Green 1out of 16 1
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RY
RYRrYyRound
yellow
ry
rY
Ry
ryrYRy
RRYYRound
yellow
RryyRoundgreen
rrYyWrinkled
yellow
rrYYWrinkled
yellow
RryyRound
green
RRyyRoundgreen
RrYYRound
yellow
RRYyRound
yellow
rryyWrinkled
green
RrYyRoundyellow
RrYyRoundyellow
RrYyRound
yellow
RRYyRoundyellow
rrYyWrinkled
yellow
RrYYRoundyellow
RRYY
RRyy
RrYY
RrYy
Rryy
rrYy
rryy
rrYY
RRYy
1
4
1
1
2
2
2
2
1
Genotype bi ti f t it (
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Genotype - gene combination for a trait(e.g.RRYY, RrYy, rryy)
Thus the Genotypic ratio is approximately 1 : 4 : 1 : 1 : 2 : 2: 2 : 2 :1
Genotype No. of squares inchequerboard
RRYY 1
RrYy 4
RRyy 1
rrYY 1
RrYY 2
RRYy 2
rrYy 2
Rryy 2rryy 1
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Mendel produced 556pea plants of which 315
had roundyellowseeds,101wrinkledyellow,
108 roundgreenseeds, 32 wrinkledgreen
seeds.
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Mendel Gained post humous
fame as the figure head of
the new science of genetics