possible pairing of
homologous chromosomes
dominant
allele
recessive
allele
location of
gene for
seed color
maternal paternal maternal paternal maternal paternal
homozygous
dominant
heterozygous
yellow seeds
yellow seeds
(a) Results of Mendel’s dihybrid cross
homozygous
recessive
green seeds
(b) Why Mendel got these results
P generation
P generation
smooth
wrinkled
yellow cross- green
pollination
x
SS YY
SY
gametes
ss yy
sy
x
gametes
F1 generation
F1 generation
100% smooth yellow
100% Ss Yy
self-fertilization
F2 generation
Pollen
Egg
SY
F2 generation
SY
Sy
sY
sy
SS YY SS Yy Ss YY Ss Yy
Sy
SS Yy SS yy Ss Yy Ss yy
sY
315
9
smooth
yellow
:
101
3
wrinkled
yellow
:
108
3
:
32
1
smooth wrinkled
green
green
Ss YY Ss Yy ss YY ss Yy
sy
Ss Yy Ss yy ss Yy ss yy
David Krogh, A BRIEF GUIDE TO BIOLOGY, 1/e © 2007 Pearson Prentice Hall, Inc.
Figures 11.8, 11.9