Download Pleiotropic genes

Figure 10.18a
Pleiotropic genes
Fruit color is highly variable in bell peppers.
Figure 10.18b
Figure 10.18c
Crosses between pure lines produce novel colors.
Model to explain 9 : 3 : 3 : 1 pattern observed above: Two genes interact to produce pepper color.
Parental
generation
Genotype
X
Yellow
Brown
Color
Explanation of color
R-Y-
Red
Red pigment + no chlorophyll
rrY-
Yellow
Yellow pigment + no chlorophyll
R-yy
Brown
Red pigment + chlorophyll
rryy
Green
F1 generation
Yellow pigment + chlorophyll
Red
Self-fertilization
F2 generation
Red
9/16
Yellow
3/16
Brown
3/16
Green
1/16
Gene 1
Gene 2
R = Red
Y = Absence of green (no chlorophyll)
r = Yellow
y = Presence of green (+ chlorophyll)
(-) = R or r
(-) = Y or y
Figure 10.20a
Kernel color is quantitative trait.
Parental
generation
Skin color
in corn
snakes
X
F2 generation
Number of each
phenotype
F1 generation
20
15
6
15
6
1
1
Phenotypes
Figure 10.20b
X
aa bb cc
(pure line white)
Model to explain
inheritance
of kernel color
AA BB CC
(pure line red)
Polydactyly
Aa Bb Cc
(medium red)
Self-fertilization
20
15
6
1 aabbcc
2 Aabbcc
2 aaBbcc
2 aabbCc
0
1
1
1 AAbbcc
4 AaBbcc
1 aaBBcc
4 AabbCc
1 aabbCC
4 aaBbCc
2
2 AABbcc
2 AAbbCc
2 AaBBcc
2 AabbCC
2 aaBBCc
2 aaBbCC
8 AaBbCc
3
15
1 AABBcc
4 AABbCc
1 AAbbCC
4 AaBbCC
1 aaBBCC
4 AaBBCc
4
6
2 AABBCc
2 AaBBCC
2 AABbCC
5
Number of red pigment alleles (A, B, or C) in genotype
1
1 AABBCC
6
Pedigree showing incomplete
penetrance
Expressivity in
beagles
• Each of these dogs has the
dominant allele for piebald
(black and white) spotting
• The degree of spotting
varies among individuals
Polydactyly
Penetrance and expressivity
Environmental
effects on fur color
in Himalayan
rabbits
Fur color
in Siamese
cats