Name: _____________________________________________________
Genetics Practice Questions ~ Biology 30:
Remember:
 Incomplete dominance is a blending of the two alleles (traits) (dominant and recessive).
o Examples:
 Red coloured snapdragons are not completely dominant over white
snapdragons and the heterozygote individual produces a pink.
 Straight, wavy and curly hair

Codominance is when both dominant alleles (traits) appear in the offspring.
o

Examples:
 Blood types in humans. Both A and B blood are dominant and produce type AB.
 Red and Blue Roan colouring in animals
 Erminette colouring in chickens (a mottled black and white colour).
Multiple Alleles is when three or more alleles are available for a specific gene. (Remember the
most one person can have at a time is ______).
o Examples:
 A, B, O blood group in humans
Genotype
Phenotype
IA IA
A
IAi
Type B
IBIB
B
IBi
Type AB
IAIB
AB
Type O
ii
O
A
** Type A (I ) is dominant over type O (i)
** Type B is dominant over type O
****Type A and B or Codominant
** Type O is recessive (ii)
Type A
Practice Questions:
1. In some chickens, the gene for feather color is controlled by codominance. The allele for
black is B and the allele for white is W. The heterozygous phenotype is known as
erminette. (Please use C as your base letter).
a. What is the genotype for black chickens? ____CB___
b. What is the genotype for white chickens? ____CW___
c. What is the genotype for erminette chickens? ___CBCW___
Name: _____________________________________________________
i)
What offspring would result from a cross of a black chicken with an erminette chicken?
Please include the genotypic and phenotypic ratios.
2. In snapdragons, yellow flowers are not completely dominant over white flowers and the
heterozygous individual produces pale yellow flowers.
a. What offspring would result from a cross of a Pale Yellow flower and a white flower?
(Please include the genotypic and phenotypic ratios.)
Name: _____________________________________________________
3. Consider human blood types…
a. What types of blood types would children from these crosses have?
i. Heterozygous A X Type O
What’s the probability of having a type A child? _________________
ii. Homozygous B X Type AB
What’s the probability of having a type AB child? _________________
iii. Heterozygous A X Heterozygous B
Name: _____________________________________________________
What’s the probability of having a type O child? _________________
iv. Type AB X O
What’s the probability of having a type B child? _________________
Dihybrid Cross with Incomplete, Codominance and Multiple Alleles
Name: _____________________________________________________
5.
Name: _____________________________________________________
6.