Name: _________________________
Date: _________________
Period: ________
Unimonster Activity
Pre-lab Discussion
How are traits inherited? You can investigate this question by considering an
imaginary animal called the unimonster. Suppose this animal has only one pair of
chromosomes. Chromosomes carry genes, which control different genetic
traits, such as hair color, height, and other physical characteristics. Different
forms of a gene are called alleles. The presence of different alleles on the
chromosomes of unimonsters determines whether they have one horn or two
horns. During reproduction, parent unimonsters pass on alleles to their
offspring.
In this investigation, you will determine the different allele combinations for
the offspring of two unimonsters and figure out the number of horns the young
unimonsters will have.
1. What are dominant and recessive alleles?
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2. Define genotype and phenotype.
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3. What does it mean to say that an organism is homozygous for a trait?
Heterozygous for a trait?
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4. How do the numbers of chromosomes in cells compare with the number of
chromosomes in sex cells? During reproduction, what fraction of chromosomes
does each parent contribute to its offspring?
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Problem
How can you determine the traits of a unimonster ’s offspring?
Materials (per group)
4 craft sticks (already labeled as shown in Figure 2)
Procedure
1. Figure 1 shows a mother and a
father unimonster, each with
different genetic traits. The allele for
two horns is dominant over the allele
for one horn.
Look at the drawing and answer
question 1 in Observations.
2. The mother unimonster is
heterozygous. This means that she has one allele for two horns and one allele
for one horn. Each of her sex cells will have either a chromosome with the twohorn allele or a chromosome with the one-horn allele.
3. One of the mother unimonster ’s chromosomes will
carry the two-horn allele. The mother unimonster ’s other
chromosome will carry the one-horn allele.
4. The father unimonster is homozygous (hh).
5. During reproduction, the sex cells produced by the
mother and father unimonsters combine to form a
fertilized egg. The fertilized egg will grow into a young
unimonster. Whether the young unimonster has one or two horns depends on
the alleles on the chromosome contributed by each parent during
reproduction. In Observations, use your chromosome models to answer
questions 2–5. Remember that the allele for two horns is dominant. Anytime the
dominant allele (H) is present, the unimonster will have two horns.
Observations
1.
Which unimonster parent has the dominant allele for number of horns?
How do you know?
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During
reproduction, the sex cells containing the chromosomes M1 and F1 combine to
form a fertilized egg.
a. Which alleles are on each of the chromosomes?
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b. Will the young unimonster have one horn or two horns? _____ Draw the
appropriate number of horns on young unimonster 1 in Figure 3.
3.
During reproduction, the sex cells containing the chromosomes M1 and F2
combine to form a fertilized egg.
a. Which alleles are on each of the chromosomes?
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b. Will the young unimonster have one horn or two horns? _____ Draw the
appropriate number of horns on young unimonster 2 in Figure 3.
4.
During reproduction, the sex cells containing the chromosomes M2 and F1
combine to form a fertilized egg.
a. Which alleles are on each of the chromosomes?
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b. Will the young unimonster have one horn or two horns? _____ Draw the
appropriate number of horns on young unimonster 3 in Figure 3.
5.
During reproduction, the sex cells containing the chromosomes M2 and F2
combine to form a fertilized egg.
a. Which alleles are on each of the chromosomes?
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b. Will the young unimonster have one horn or two horns? ____ Draw the
appropriate number of horns on young unimonster 4 in Figure 3.
Analyze and Conclude
1.
Which young unimonster(s) are homozygous and have one horn?
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2.
Which young unimonster(s) are heterozygous?
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3.
Are any young unimonster(s) homozygous with two horns? Explain.
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Critical Thinking and Applications
1.
If a mother unimonster is homozygous and has two horns, and a father
unimonster is homozygous and has one horn, what are the phenotypes and
genotypes of the possible offspring? Remember that the two-horn allele is
dominant.
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2.
Predict the phenotypes and genotypes of the offspring of a
mother unimonster and a father unimonster that are both heterozygous.
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More to Explore
Assume that a curly-hair allele is dominant and a straight-hair allele is recessive.
The mother is homozygous and has straight hair, while the father is
heterozygous. Use the Punnett Square below to find all of the possible
genotypes and resulting phenotypes of the offspring.
Possible genotype(s):
Possible phenotype(s):