Download Biology B - Fort Bend ISD

Name:_______________________________________ Date:___________________ Period:________
Incomplete Dominance Crosses: Considers the inheritance of alleles in a situation in which one allele
is not completely dominant over another; the phenotype is a “blending” of the two alleles.
1.
In some birds, a cross between a blue colored bird (BB) and a white colored bird (WW) produces
offspring that are silver (BW). The color of the birds is determined by just two alleles. Determine
the genotype and phenotype ratios below for a cross between a blue bird and white bird.
a.
b.
c.
d.
e.
What is the genotype of the blue colored bird? _____________________________
What is the genotype of the white colored bird? ____________________________
Draw a Punnett square for this mating to determine the ratios below.
What are the genotypes of the offspring? _____________________________
What are the phenotypes of the offspring? _____________________________
1. Draw a Punnett square for a mating between two silver colored birds to determine the ratios below.
a. What is the probability of having a blue bird in the F1 generation? _____________________
b. What is the probability of having a silver bird in the F1 generation? _____________________
SpongeBob loves growing flowers for his pal Sandy. Her favorite flowers, Poofkins, are found in
red (CC), blue (BB) and purple (CB). When red and blue flowers are mixed, they produce purple
flowers.
2. What would happen if SpongeBob crossed a red Poofkin with a blue Poofkin? Complete the Punnett square to
determine the genotype and phenotype ratios.
a. What is the genotype of the red Poofkin? ________________
b. What is the genotype of the blue Poofkin? ________________
i. F1 genotype ratios: __________________________
ii. F1 phenotype ratios: ________________________
3. What would happen if SpongeBob crossed two purple Poofkins? Complete a Punnett square to determine the
probabilities below.
i. What is the probability of having a red Poofkin from this cross? ________________
ii. What is the probability of having a purple Poofkin from this cross? _______________
4. What would happen if SpongeBob crossed a purple Poofkin with a blue Poofkin? Complete the Punnett square
to determine the phenotype and genotype ratios.
a. What is the genotype of the purple Poofkin? ________________
b. What is the genotype of the blue Poofkin? ________________
i. F1 genotype ratios: __________________________
ii. F1 phenotype ratios: ________________________
c. If SpongeBob planted 100 seeds from this cross, how many should he expect to have of each color?
Purple flowers - ____________
Blue Flowers - _____________ Red Flowers - ___________
Codominance Crosses: Considers the inheritance of alleles in a situation in which both alleles of a
gene contribute to the phenotype of the organism; both alleles are expressed but NOT blended.
1. A cross between a homozygous black cat (BB) and a homozygous tan cat (TT) produces a tabby pattern (black
& tan fur together) (BT). Complete a punnett square to determine the following ratios for the possible
offspring if a black and tan cat are mated.
a. What is the genotype of the black cat? _______________________
b. What is the phenotype of the black cat? _______________________
c. What is the genotype of the tan cat? _______________________
d. What is the phenotype of the tan cat? _______________________
e. What is the F1 genotypic ratio? ________________________________
f.
1.
What is the F1 phenotypic ratio? _______________________________
Draw a Punnett square for crossing a tabby cat with a black cat.
a. What are the genotypic ratios? ________________________________
b. What are the phenotypic ratios?
_________________________________
c. What percentage of kittens would have tan fur if a tabby cat is crossed with a black cat?
_______________________
Sex Linked Traits: Are traits that are determined by alleles that are found on the X and Y chromosome.
1. Humans are able to detect color because of a dominant gene carried on the X chromosome. The
recessive allele produces red-green color blindness. A man with normal color vision marries a female
who carries a recessive gene, although her vision is normal.
a.
What is the phenotype of the female? __________________________
b.
What is the genotype of the female? __________________________
c.
What is the phenotype of the male? __________________________
d.
What is the genotype of the male? __________________________
e. What are the chances (%) they will have a colorblind daughter? ________________
f. What are the chances (%) they will have a daughter with normal vision? ________________
g. What are the chances (%) they will have a son with normal vision? ________________
h. What are the chances (%) they will have a colorblind son? ________________
2. A hybrid (heterozygous) woman from the previous cross marries a colorblind male producing the F2
generation of offspring.
a. What is the genotype of the woman? _________________________
b. What is the genotype of the man? _________________________
c. What are all possible F2 male genotypes? _______________________
d. What are all possible F2 male phenotypes? _______________________
Punnett squares worksheet
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e. What are all possible F2 female genotypes ______________________
f. What are all possible F2 female phenotypes? _____________________
3. One of the sons from the previous mating is involved in a paternity suit. The child in question is a
colorblind female. The judge rules that the child could not possibly belong to this man.
a. Which son of the parents in problem 2 was involved in this case? Give his genotype and
phenotype. _____________________________________
b. Explain your answer.
________________________________________________________________
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4. If a woman is a carrier for a mutation causing a sex-linked disorder, what is the chance that one of her
sons will have the disorder? Explain your answer.
________________________________________________________________
________________________________________________________________
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5. If a man has a sex-linked disorder, what is the chance that he will pass it on to one of his sons?
Explain.
________________________________________________________________
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Blood typing: Blood types are determined by multiple alleles (IA, IB, and i). Two of the alleles are also
codominant (IA and IB) whereas O blood type is completely recessive (ii)
1.
A man who has AB blood marries a woman with O blood.
a.
What is the phenotype of the female? __________________________
b.
What is the genotype of the female? __________________________
c.
What is the phenotype of the male? __________________________
d.
What is the genotype of the male? __________________________
e.
What is the genotype ratio of the offspring? ___________________________
f.
What is the phenotype ratio of the offspring? ___________________________
2. Both Mrs. Smith and Mrs. Jones had babies the same day in the same hospital. Mrs. Smith took a
baby girl home, whom she named Shirley. Mrs. Jones took a baby girl home, whom she named Jane.
However, Mrs. Jones began to suspect that her child had been accidentally switched with the Smith
baby in the nursery. Blood tests were made: Mr. Smith was Type-A, Mrs. Smith was Type-B, Mr.
Jones was Type-A, Mrs. Jones was Type-A. Shirley was Type-O and Jane was Type-B.
1) Did a mix-up occur? _________________________________________
2) Explain your answer. (Use Punnett Squares help you explain.)
________________________________________________________________
________________________________________________________________
________________________________________________________________
Punnett squares worksheet
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2.
If a man with blood Type-B, one of whose parents had blood Type-O, marries a woman with
blood Type-AB.
a. What percentage of their children should have blood Type-B? _________ %
3.
A man with Type-O blood married a woman with Type-AB get married. One of their children
needs an operation. This child has Type-B blood.
a. Can the child safely receive a blood transfusion from either parent? Explain.
________________________________________________________________
________________________________________________________________
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Polygenic Crosses: Considers the inheritance of traits that are determined by alleles from more
than one gene; these traits usually have many phenotypes.
6.
Labrador retrievers can have coat colors that are black, chocolate or yellow. Coat color is
determined by two genes, E and B. If a dog carries at least one dominant allele for both genes,
the coat color is black. If a dog has at least one dominant allele for E but is homozygous
recessive for gene B, the coat color is chocolate. If a dog has is homozygous recessive for gene
E, its coat is yellow regardless of the genotype for gene B.
Two dogs heterozygous for both genes are crossed.
__________________ x __________________
a.
What are the genotypes of the dogs? __________________________
b.
What is the phenotype of the dogs? __________________________
c.
How many different types of gametes can be formed by each dog? _______
i. The genotypes of the gametes are: __________________________
d.
Draw a Punnett square for this mating below.
e.
What is the F1 genotypic ratio? __________________________
f.
What is the F1 phenotypic ratio? __________________________
Punnett squares worksheet
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