Principles of Plant Genetics and Breeding

44 CHAPTER 3
AB
Ab
aB
ab
(a)
Parents
Gametes
F 1
Gametes
F 2
A
B
A
B
A
B
A
B
A
B A B
Ab
AABb
AAbb
AaBb
Aabb
(a) Complementary genes 9 : 7
AB
Ab
aB
ab
AB
AABB
AABb
AaBB
AaBb
(c) Duplicate genes 15 : 1
AB
Ab
aB
ab
AB
AABB
AABb
AaBB
AaBb
AB
AABB
AABb
AaBB
AaBb
Ab
AABb
AAbb
AaBb
Aabb
Ab
AABb
AAbb
AaBb
Aabb
(e) Dominant epistasis 12 : 3 : 1
A
B
a
b
A
B
×
a
b
a A
b B
A
B
a
b
aB
AaBB
AaBb
aaBB
aaBb
aB
AaBB
AaBb
aaBB
aaBb
aB
AaBB
AaBb
aaBB
aaBb
a
b
Male Female
a
b a b
a
b
a
b
a
b
ab
AaBb
Aabb
aaBb
aabb ab AaBb Aabb
ab
AaBb
Aabb
aaBb
Figure 3.8 Epistasis or non-Mendelian inheritance is manifested in a variety of ways, according to the kinds of interaction.
Some genes work together while other genes prevent the expression of others.
Figure 3.9 Genetic linkage. (a) Linked genes AB/ab are transmitted intact from one generation to the next.
(b) Genetic linkage may be broken by the process of recombination. A testcross may be used to reveal the occurrence
of recombination. Recombinants are the individuals that are derived from gametes with crossovers.
AB
Ab
aB
AB
AABB
AABb
AaBB
(b) Additive genes 9 : 6 : 1
(b)
A
b
A
b
Ab
AABb
AAbb
AaBb
aabb ab AaBb Aabb
ab
AaBb
Aabb
aaBb
AB
Ab
aB
(d) Suppressor genes 13 : 3
AB
Ab
aB
AB
AABB
AABb
AaBB
AB
AABB
AABb
AaBB
Ab
AABb
AAbb
AaBb
Ab
AABb
AAbb
AaBb
aabb ab AaBb Aabb
(f) Recessive epistasis 9 : 3 : 4
a
b
A
B
a
B
a
B
a
b
A
B
a
b
×
A
B
aB
AaBB
AaBb
aaBB
aaBb
aB
AaBB
AaBb
aaBB
aaBb
aB
AaBB
AaBb
aaBB
aaBb
a
b
a
b
Crossover Noncrossover
a
b
a
b
a
b
Recombinants Parental
genotypes
a
b
a
b
ab
AaBb
Aabb
aaBb
aabb
ab
AaBb
Aabb
aaBb
aabb
ab
AaBb
Aabb
aaBb
aabb
Parents
Gametes
F 1