mapping of genes

7/29/2019 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

.


CHEQUERBOARD

PHENOTY

PIC RATIO


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

.


CHEQUERBOARD

PHENOTY

PIC RATIO



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

.


CHEQUERBOARD

PHENOTY

PIC RATIO



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

mapping of genes

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