Download Multiple Gene (Polygenic) Inheritance

Polygenic Inheritance
Human skin color is a good example of polygenic (multiple gene) inheritance. Assume
that three "dominant" capital letter genes (A, B and C) control dark pigmentation
because more melanin is produced.
The "recessive"alleles of these three genes (a, b & c) control light pigmentation because
lower amounts of melanin are produced.
(AABBCC) has the maximum amount of melanin and very dark skin.
A genotype with all "recessive" small case genes (aabbcc) has the lowest amount of
melanin and very light skin.
AaBbCc has a medium amount of melanin and an intermediate skin color.
AaBbCc x AaBbCc
Each parent produces eight different types of gametes.
The skin colors can be represented by the number of capital letters, ranging from zero
(no capital letters) to six (all capital letters).
Gametes ABC
ABC
ABc
AbC
Abc
aBC
aBc
abC
abc
ABc
AbC
Abc
aBC
aBc
abC
abc
Gametes ABC
ABc
AbC
Abc
aBC
aBc
abC
abc
ABC
ABc
AbC
Abc
aBC
aBc
abC
abc
The offspring contain seven different shades of skin color based on the number of
capital letters in each genotype.