Download simple genetic crosses

SIMPLE GENETIC CROSSES
Before you begin we need to learn the steps of performing a genetic crosses.
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Genotype of parent 1 (genetics)
Genotype of parent 2 (genetics)
Phenotype of parent 1 (physical trait)
Phenotype of parent 2 (physical trait)
Write the cross out ____ x ____
Construct and solve the punnett square
Genotypic ratio (genetics)
Phenotypic ratio (physical trait)
KEY: T = Tall
Tt X TT
t = Short
TT X TT
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Tt X tt
Tt X Tt
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What is a genotype? Give an example _____________________________________
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What is a phenotype? Give an example ____________________________________
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Use the key: C = curly hair c= straight hair. Write out the genotype and phenotype
of the individuals below
Genotype
Phenotype
Pure dominant
___________
___________________
Heterozygous
___________
___________________
Pure recessive
___________
___________________
Hybrid
___________
___________________
Homozygous recessive
___________
___________________
Homozygous dominant
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___________________
Use the 8 steps of genetic problem solving to determine the genotype
and phenotype ratios of the offspring in the problems below.
1. Long wings are dominant to short wings. If a heterozygous male is
crossed with a
heterozygous female, describe the
offspring produced.
2. Yellow is dominant and green is recessive in seed color. Cross a
heterozygous seed with a green seed. What are the phenotypes and
genotypes of the offspring?
3. Diabetes is a recessive trait. An individual must have both
recessive alleles for diabetes in order to have the disorder. If a
diabetic man marries a homozygous woman who is not diabetic, what
are the genotypes and phenotypes of their offspring?
4. In humans, the gene for brown eyes is dominant to that for blue
eyes. A man with blue eyes marries a brown-eyed woman whose mother
had blue eyes. What proportions of the children would be expected
to have blue eyes?
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A female Guinea pig has had babies (86). 42 are black and the
rest are white. Please
determine the genotype and phenotypes of the
parents. Black is dominant. Work
backwords for this
problem.
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In humans, the ability to taste P.T.C. is determined by the
dominant gene T.
A non-taster man both of whose parents were
tasters married a taster woman whose father was a homozygous
taster and mother a non-taster. They have one child who is a
non-taster. What are the genotypes of the individuals mentioned?
(You do NOT need to complete the 8 steps for this problem.)
INCOMPLETE DOMINANCE
PROBLEMS
Use the 8 steps of genetic problem solving to determine the genotype
and phenotype ratios of the offspring in the problems below.
Oompahs can have red, blue, or purple hair. The allele that controls
this trait shows incomplete dominance, and purple hair is caused by
the heterozygous condition.
1. Orville Oompah has purple hair and is married to Opal Oompah, who
brags that she has the bluest blue hair in the valley. How many of
Opals children will be able to brag about their blue hair also.
2. One of Opal’s children is born with shocking red hair. Is Orville
Oompah the father of this child? Show a Punnett square to support
yes or no. But wait, Opal swears that she has been faithful, she
claims the hospital goofed and got her baby mixed up with someone
else’s. Based on genetics, is this a likely story? Explain.
3. Olga Oompah has red hair and married Oliver Oompah who has purple
hair. They have 32 children. What is the hair color of their
children and in what proportion?
4. Olivia Oompah is married to Odo Oompah. Olivia has red hair and
Odo has blue hair. They have 100 children. What is the hair color
of their children and in what proportion?
What are the genotype and phenotype ratios of Olivia and Odo’s
grandchildren (F2
generation)?
5. In the land of Oompah, blue hair is highly valued. Blue haired
Oompahs get special benefits. Oscar Oompah has purple hair but he
wants a wife that will give him children with blue hair. What
color hair should he look for in a wife? If he can’t find this
type of Oompah what should be his second choice?
Determine the genotype and phenotype ratios of the offspring in the problems below
1. What are the genotypes for the following individuals having….
Heterozygous A blood ________
Homozygous A blood _________
Heterozygous B blood ________
Homozygous B blood _________
Type O blood _________
Type AB blood _________
2. Cross a female with AB blood and a male with AB blood. What are the genotypes and
phenotypes of their offspring?
3. A man with type O blood marries a woman that is homozygous for B blood. Give the
possible genotypes and phenotypes of their offspring.
4. If a man with homozygous A blood marries a woman with heterozygous B blood, what are
the genotypes and phenotypes of their offspring?
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Cross a man with AB blood and a woman with O blood. Describe the ratios of their
offspring.
4. Somehow there was a mix up at the hospital nursery and the identity of two babies is
uncertain. Using the information below, determine which baby belonged to which parents.
(you may need to do two punnett squares)
Baby #1= Type B blood
Baby #2= Type AB blood
Mr. and Mrs. Johnson have Type AB and O blood
Mr. and Mrs. Davis have Type B and Type A blood.
5. If one parent has Type B blood and the other has Type A blood, complete the punnett square
that will produce children with the following blood types:
a. 50% AB and 50% A
Parents Genotypes: ________/_________
b. 25% A, 25% B, 25% AB, 25% O
Parents Genotypes: ________/_________
c. All AB
Parents Genotypes: ________/_________
6. Complete a punnett square that will produce only children with Type O blood.