R Mother Rr Female gametes R r Father Rr Male gametes R r Rr RR Rr rr Resulting genotypes: 1/4 RR : 1/2 Rr : 1/4 rr Resulting phenotypes: 3/4 : 1/4 Figure 10.7 R = Dominant allele for seed shape (round) r = Recessive allele for seed shape (wrinkled) = Round-seeded phenotype = Wrinkled-seeded phenotype
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R Mother Rr Female gametes R r Father Rr Male gametes R r RrRR Rrrr Resulting genotypes: 1/4 RR : 1/2 Rr : 1/4 rr Resulting phenotypes: 3/4 : 1/4 Figure.
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R
Mother
Rr
Female gametes
R r
Father
Rr
Mal
e g
ame
tes R
r
RrRR
Rr rr
Resulting genotypes: 1/4 RR : 1/2 Rr : 1/4 rr
Resulting phenotypes: 3/4 : 1/4
Figure 10.7
R = Dominant allele for seed shape (round)r = Recessive allele for seed shape (wrinkled)
Crosses Between Plants that Differ in One Trait Identifies A Fundamental Pattern in Genetics
Mendel develops Principle of Segregation
• The two alleles of each gene must segregate into different gamete cells during the formation of eggs and sperm in the parent.
Dominant allelefor seed shape(round)
R r Recessive allelefor seed shape(wrinkled)
Chromosomes replicate
R R r r
Meiosis I
r rR R
Meiosis II
r rRR
Gam
etes
Figure 10.11a
Principle of segregation
Figure 10.8a
R = Dominant allele for seed shape (round)r = Recessive allele for seed shape (wrinkled)
Y = Dominant allele for seed color (yellow)
y = Recessive allele for seed color (green)
Father MotherParentalgeneration
Gametes
Meiosis
Fertilization
F1 generation
Cross peas that differ in two traits
F2 generationphenotype
Number 315 101 108 32 = 556
Fraction ofprogeny 9/16 3/16 3/16 1/16 = 1
Figure 10.8b
Self-fertilize F1 peas and count F2 offspring
3 : 1
3 : 1
423 : 133
315 + 108 : 101 + 32
Round seeds : Wrinkled seeds
How does the 9 : 3 : 3 : 1 ratio observed for two traitsrelate to the 3 : 1 ratio observed for one trait?
416 : 140
315 + 101 : 108 + 32
Yellow seeds : Green seeds
Figure 10.8c
Parentalgeneration
F1
generationALL
RrYy
rryy
RrYy
Female gametes
RRYY
1/4 RY 1/4 Ry 1/4 rY 1/4 ry
R = Dominant allele for seed shape (round) r = Recessive allele for seed shape (wrinkled)Y = Dominant allele for seed color (yellow) y = Recessive allele for seed color (green)