1. technique results parental generation (p) stamens carpel 1 2 3 4 first filial gener- ation...
TRANSCRIPT
TECHNIQUE
RESULTS
Parentalgeneration(P) Stamens
Carpel
1
2
3
4
Firstfilialgener-ationoffspring(F1)
5
2
EXPERIMENT
P Generation
(true-breeding parents) Purple
flowers Whiteflowers
F1 Generation
(hybrids) All plants hadpurple flowers
F2 Generation
705 purple-floweredplants
224 white-floweredplants
3
Allele for purple flowers
Homologouspair ofchromosomes
Locus for flower-color gene
Allele for white flowers
5
P Generation
Appearance:Genetic makeup:
Gametes:
Purple flowers White flowersPP
P
pp
p
F1 Generation
Gametes:
Genetic makeup:Appearance: Purple flowers
Pp
P p1/21/2
F2 Generation
Sperm
Eggs
P
PPP Pp
p
pPp pp
3 1
6
Phenotype
Purple
Purple3
Purple
Genotype
1 White
Ratio 3:1
(homozygous)
(homozygous)
(heterozygous)
(heterozygous)
PP
Pp
Pp
pp
Ratio 1:2:1
1
1
2
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TECHNIQUE
RESULTS
Dominant phenotype, unknown genotype:
PP or Pp?
Predictions
Recessive phenotype, known genotype: pp
If PP If Ppor
Sperm Spermp p p p
P
P
P
p
Eggs Eggs
Pp
Pp Pp
Pp
Pp Pp
pp pp
or
All offspring purple 1/2 offspring purple and1/2 offspring white
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EXPERIMENT
RESULTS
P Generation
F1 Generation
Predictions
Gametes
Hypothesis ofdependentassortment
YYRR yyrr
YR yr
YyRr
Hypothesis ofindependentassortment
orPredictedoffspring ofF2 generation
Sperm
Sperm
YR
YR
yr
yr
Yr
YR
yR
Yr
yR
yr
YRYYRR
YYRR YyRr
YyRr
YyRr
YyRr
YyRr
YyRr
YYRr
YYRr
YyRR
YyRR
YYrr Yyrr
Yyrr
yyRR yyRr
yyRr yyrr
yyrr
Phenotypic ratio 3:1
EggsEggs
Phenotypic ratio 9:3:3:1
1/21/2
1/2
1/2
1/4
yr
1/41/4
1/41/4
1/4
1/4
1/4
1/43/4
9/163/16
3/161/16
Phenotypic ratio approximately 9:3:3:1315 108 101 32
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Rr RrSegregation of
alleles into eggs
Sperm
R
R
R RR
R rrr
r
r
r1/2
1/2
1/2
1/2
Segregation ofalleles into sperm
Eggs1/4
1/4
1/41/4
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Red
P Generation
Gametes
WhiteCRCR CWCW
CR CW
F1 GenerationPinkCRCW
CR CWGametes 1/21/2
F2 Generation
Sperm
Eggs
CR
CR
CW
CW
CRCR CRCW
CRCW CWCW
1/21/2
1/2
1/2
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IA
IB
i
A
B
none(a) The three alleles for the ABO blood groups and their associated carbohydrates
Allele Carbohydrate
GenotypeRed blood cell
appearancePhenotype
(blood group)
IAIA or IA i A
BIBIB or IB i
IAIB AB
ii O
(b) Blood group genotypes and phenotypes
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BbCc BbCc
Sperm
EggsBC bC Bc bc
BC
bC
Bc
bc
BBCC
1/41/4
1/41/4
1/4
1/4
1/4
1/4
BbCC BBCc BbCc
BbCC bbCC BbCc bbCc
BBCc BbCc
BbCc bbCc
BBcc Bbcc
Bbcc bbcc
9 : 3 : 4
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Eggs
Sperm
Phenotypes:
Number ofdark-skin alleles: 0 1 2 3 4 5 6
1/646/64
15/6420/64
15/646/64
1/64
1/8
1/8
1/8
1/8
1/8
1/8
1/8
1/8
1/81/8
1/81/8
1/81/8
1/81/8
AaBbCc AaBbCc
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KeyMale
Female
AffectedmaleAffectedfemale
Mating
Offspring, inbirth order(first-born on left)
1st generation(grandparents)
2nd generation(parents, aunts,and uncles)
3rd generation(two sisters)
Ww ww ww Ww
Ww ww ww Ww Ww ww
ww
Ww
WWor
Widow’s peak No widow’s peak(a) Is a widow’s peak a dominant or recessive trait?
1st generation(grandparents)
2nd generation(parents, aunts,and uncles)
3rd generation(two sisters)
Ff Ff Ff
Ff FfFfFF or ff ff
ff
ff
ff FForFf
Attached earlobe Free earlobe
(b) Is an attached earlobe a dominant or recessive trait?
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Amniotic fluidwithdrawn
Fetus
Placenta
Uterus Cervix
Centrifugation
Fluid
Fetalcells
Severalhours
Severalweeks
Severalweeks
(a) Amniocentesis (b) Chorionic villus sampling (CVS)
Severalhours
Severalhours
Fetalcells
Bio-chemical
tests
Karyotyping
Placenta Chorionicvilli
Fetus
Suction tubeinsertedthroughcervix
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Degree of dominance
Complete dominanceof one allele
Incomplete dominanceof either allele
Codominance
Description
Heterozygous phenotypesame as that of homo-zygous dominant
Heterozygous phenotypeintermediate betweenthe two homozygousphenotypes
Heterozygotes: Bothphenotypes expressed
Multiple alleles
Pleiotropy
In the whole population,some genes have morethan two alleles
One gene is able toaffect multiplephenotypic characters
CRCR CRCW CWCW
IAIB
IA , IB , i
ABO blood group alleles
Sickle-cell disease
PP Pp
Example
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