INCOMPLETE DOMINANCE, CODOMINANCE, MULTIPLE ALLELES
Incomplete Dominance
The color of the flowers of a snapdragon plant illustrates incomplete dominance. Two alleles are present for color--red (F) and white (F’). However, when a red
flowered plant is crossed with a white flowered plant a PINK flowered plant is the result.
1.
2.
3.
4.
Write the genotype that would result in a (A) Red Flower
(B) White Flower
Cross a red flowered plant and a white flowered plant. Give genotypic & phenotypic ratios.
Cross a red flowered plant with a pink flowered plant. Give genotypic & phenotypic ratios.
Cross two pink flowered plants. Give genotypic & phenotypic ratios.
(C)Pink Flower
Codominance
In Andalusian fowl, the gene for black plumage (AB) is codominant to the gene for white plumage (AW).
The heterozygous genotype results in expression of the black and white feathers and is referred to as blue plumange.
1.
2.
3.
4.
Write the genotype that would result in (A) black plumage (B) white plumage (C) blue plumage
Cross a fowl with black plumage with a fowl with blue plumage. Give genotypic & phenotypic ratios.
Cross two fowls with blue plumage. Give genotypic & phenotypic ratios.
Cross a fowl with blue plumage with a fowl with white plumage. Give genotypic & phenotypic ratios.
Multiple Alleles
In humans, there are different alleles which code for blood type. Two are dominant and code for specific antigens on the blood cells. IA is the allele for antigen A, IB
is the allele for antigen B, and i is the recessive allele which codes for no antigen.
1. Using the alleles above write all the possible genotypes for a person with
(a) Type A blood
(b) Type B blood
(c) Type AB blood
(d) Type O blood
2. One parent has type A blood and the other parent has type B blood. What are their genotypes if they produce offspring with the following ratios?
(a) all AB
(b) 1/2 AB and 1/2 B
(c) 1/2 AB and 1/2 A
(d) 1/4 AB, 1/4 A, 1/4 B, 1/4 O
Application Problems
1. Yellow guinea pigs crossed with white ones always produce cream colored offspring (the hair is actually cream colored). Two cream colored pigs produce yellow,
cream, and white offspring in the ratio of 1 yellow:2 cream:1 white. How are these colored inherited?
2. In chickens when a bird with black feathered chicken is crossed with a white feathered chicken and chicken with black and white feathers is the result (called an
ermine chicken). What mode of inheritance does this represent?
3. A woman with blood type B has a child with blood type O. What are the genotypes of the mother and child? What genotypes could the father NOT have?
INCOMPLETE DOMINANCE, CODOMINANCE, MULTIPLE ALLELES
Incomplete Dominance
The color of the flowers of a snapdragon plant illustrates incomplete dominance. Two alleles are present for color--red (F) and white (F’). However, when a red
flowered plant is crossed with a white flowered plant a PINK flowered plant is the result.
1.
2.
3.
4.
Write the genotype that would result in a (A) Red Flower
(B) White Flower
Cross a red flowered plant and a white flowered plant. Give genotypic & phenotypic ratios.
Cross a red flowered plant with a pink flowered plant. Give genotypic & phenotypic ratios.
Cross two pink flowered plants. Give genotypic & phenotypic ratios.
(C)Pink Flower
Codominance
In Andalusian fowl, the gene for black plumage (AB) is codominant to the gene for white plumage (AW).
The heterozygous genotype results in expression of the black and white feathers and is referred to as blue plumange.
1.
2.
3.
4.
Write the genotype that would result in (A) black plumage (B) white plumage (C) blue plumage
Cross a fowl with black plumage with a fowl with blue plumage. Give genotypic & phenotypic ratios.
Cross two fowls with blue plumage. Give genotypic & phenotypic ratios.
Cross a fowl with blue plumage with a fowl with white plumage. Give genotypic & phenotypic ratios.
Multiple Alleles
In humans, there are different alleles which code for blood type. Two are dominant and code for specific antigens on the blood cells. IA is the allele for antigen A, IB
is the allele for antigen B, and i is the recessive allele which codes for no antigen.
1. Using the alleles above write all the possible genotypes for a person with
(a) Type A blood
(b) Type B blood
(c) Type AB blood
(d) Type O blood
2. One parent has type A blood and the other parent has type B blood. What are their genotypes if they produce offspring with the following ratios?
(a) all AB
(b) 1/2 AB and 1/2 B
(c) 1/2 AB and 1/2 A
(d) 1/4 AB, 1/4 A, 1/4 B, 1/4 O
Application Problems
1. Yellow guinea pigs crossed with white ones always produce cream colored offspring (the hair is actually cream colored). Two cream colored pigs produce yellow,
cream, and white offspring in the ratio of 1 yellow:2 cream:1 white. How are these colored inherited?
2. In chickens when a bird with black feathered chicken is crossed with a white feathered chicken and chicken with black and white feathers is the result (called an
ermine chicken). What mode of inheritance does this represent?
3. A woman with blood type B has a child with blood type O. What are the genotypes of the mother and child? What genotypes could the father NOT have?