Download Incomplete Dominance, Codominance, and Multiple Alleles **Work

Incomplete Dominance, Codominance, and Multiple Alleles
**Work must be shown for every question
1. Explain the difference in incomplete dominance, codominance, and multiple alleles.
Incomplete Dominance
1. This problem involves two gerbils named Cheese and Ritz. The gene in question is a fur color
gene which has 2 alleles – brown (B) and black (b). The heterozygous form produces a honey
colored fur. If we crossed Cheese (with brown fur) and Ritz (with honey fur), what is the chance
of them having offspring with black fur?
2. In Mendel’s experiments, if the gene for tall (T) plant was incompletely dominant with the gene
for short (t) plants, what would be the genotype and phenotype ratios resulting from crossing a
short plant with a heterozygous plant.
3. Mom has curly hair (HH) and Dad has wavy hair (Hh). Is it possible for them to have a child with
straight hair?
Codominance
1. In a certain cactus, prickly spines can be two pronged or one pronged. If the genotype is
heterozygous, the cactus will have both one and two pronged spines. If a true breeding onepronged cactus is crossed with a true breeding two-pronged cactus, what will be the phenotype
of the offspring?
2. If you were to cross the offspring from question 1, how many of the F2 generation would have 1
pronged spines?
3. Coat color in cats is a codominant trait. Cats can be black, yellow, or calico (both yellow and
black). A female calico cat is crossed with a male black cat. What are the phenotypes of the
offspring and in what proportion?
Multiple alleles
1. Human blood types are determined by genes that follow codominance and multiple allele
patterns of inheritance. There are 2 dominant alleles (IA and IB) and one recessive allele. Fill out
the chart below using that information.
Blood type (phenotype) Possible genotypes
Can donate blood to Can receive blood from
O
AB
A
B
2. Write the genotype for each person based on the description:
a. Homozygous for the B allele ________
b. Heterozygous for the A allele ________
c. Type A blood and had a type O parent _______
d. Blood that can be donated to anybody _______
e. Can only get blood from type “O” donor ______
3. What are the possible genotypes and phenotypes of the offspring produced by a type “B”
mother and a type “A” father? (Hint: There is more than 1 way to have A and B blood so you
may need more than 1 Punnett square)
4. Based on the information in this table, which man/men could not be the father of the baby?
Justify with Punnett squares showing why these man/men could not be the father.
Name
Blood type
Mother
Type O
Baby
Type B
Suspected Father
Type O
Cable Guy
Type AB
Mailman
Type B
Suspected Father’s brother
Type A
5. Explain why blood type data can prove who the father is not but cannot prove who the father is.