26 Jun If Mendel had only looked at a single cross
Question
Name ________________________________ Class _______ Date _________________
Introduction to Genetics
Introduce yourself to the virtual Genetics lab
room to discover how pea plants display
Mendelian inheritance patterns.
Lab Bench Used
Gregor Mendel’s meticulous work with pea plants allowed him to discover patterns of
inheritance in sexually reproducing organisms. In this introductory virtual lab
activity, you can simulate some of Mendel’s crosses and data analyses.
Enter the Virtual Bio Lab and select the title of this lab activity from the “Heredity”
menu on the whiteboard. You will be taken to the virtual Genetics lab room.
Part A: The Virtual Genetics Lab Room
The virtual Genetics lab room lets you perform virtual crosses between males and
females of a variety of model species to determine how different traits are inherited.
By default, the pea plant lab environment will appear. In some activities you may be
working with human traits, in which case the settings will look like a physician’s
office. When working with other animal species, the lab will again look different.
First Generation
Select “Pea Plant” from the Species Selector. In the box on the lower left part of your
screen labeled “Experiment Setup,” select “Seed Shape” as the trait to explore.
The Genetics lab lets you set each parent’s genotype for the selected trait and then
perform an unlimited number of crosses to determine how a particular trait is passed
on to the next generation. The simulation limits the number of offspring per cross to a
realistic number for the species in question, however. In the lower left corner of the
“Experiment Setup” box, set “Number of Offspring” to 10.
Now, set one parental pea plant’s genotype as homozygous for “Wrinkled” and
the other’s genotype as heterozygous. To set a genotype, pull down on each of the
dropdown menus below a given parent.
Next, click the “Cross” button. The results of your crosses will be displayed in the
“Results” boxes to the right of the experiment setup screen. Under the headings
“Parents” and “F1 Offspring,” you will see the individuals listed using names such as
MF1, MF2, and so on. (MF1 means male-female number 1—the first offspring,
which has both male and female reproductive organs.) To check the phenotypes of an
individual offspring, roll over any of the offspring names. In the window that
appears, the phenotype of the offspring is shown in the first of three boxes and
described to the left. The phenotypes of the parents are shown in the other two boxes.
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Virtual Lab
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Heredity
Introduct toGenetics
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Name ________________________________ Class _______ Date _________________
In the “By Generation” results panel, you will find the proportional breakdown of the
phenotypes displayed by the first (F1) generation of ten offspring. The values given at
the far right side of the horizontal bar graphs (“Round” and “Wrinkled”) tell you
what proportions of that generation have a particular phenotype. For example, if 0.70
of offspring are wrinkled, that means 70% are wrinkled.
1. In data table below, write the proportions of the two phenotypes as displayed by
the first ten offspring. Then, click the “Cross” button again, to simulate the
production of 10 more offspring. Record the new phenotype proportions (for 20
offspring) in the next row. Repeat this process until the parents have produced 100
offspring.
Results of Cross
When F1 generation
consists of…
Proportion with round seed
phenotype is…
Proportion with wrinkled
seed phenotype is…
10 offspring
20 offspring
30 offspring
40 offspring
50 offspring
60 offspring
70 offspring
80 offspring
90 offspring
100 offspring
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Virtual Lab
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Heredity
Introduct toGenetics
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Name ________________________________ Class _______ Date _________________
2. What happened to the proportions of the two phenotypes as the F1 generation
grew from 10 to 100 offspring? Why?
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3. If Mendel had only looked at a single cross that produced ten offspring to
determine the pattern of inheritance of seed shape in pea plants, what might he
have inferred?
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4. How can two parents with only one “round” allele between them—only 1 out of 4
alleles—produce an F1 generation in which 50% of individuals have round seeds?
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Next Generation
In the lower middle of the “Experiment Setup” box, click “Next Generation.” Select
“Manual Crosses.” You will now be able to choose parents for the next generation
(F2) in the dropdown menus under “Parent 1” and “Parent 2.” You can choose which
F1 offspring to use as parents by rolling over the list of the F 1 offspring in the
“Results” box in the middle of the screen. Note which F1 offspring are wrinkled, then
choose two of those names from the menus under “Parent 1” and “Parent 2” to pair
them up them for mating.
5. Click the “Cross” button a few times to produce the F 2 generation. What are the
results? Do the results support the idea that pea plant seed shape has a
dominant/recessive pattern of inheritance? Explain your reasoning.
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Virtual Lab
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Heredity
Introduct toGenetics
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Name ________________________________ Class _______ Date _________________
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Part B: Pod Shape
Click the “Reset” button in the lower right corner of the “Experiment Setup” box.
Keeping pea plants as the subject, select “Pod Shape” as the trait you will investigate
next. Cross a parent that is homozygous for “Constricted” pod shape with a
heterozygote. Once again, repeat the cross until the parent plants have produced 100
offspring.
6. Look at the results of your crosses. Does it appear that pod shape is a
dominant/recessive trait? If so, which allele is dominant, and which is recessive?
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7. If you were a pea farmer and you had to produce both the constricted and the
inflated varieties of peas to satisfy the market, how would you go about ensuring
that your plants would produce adequate amounts of both types? (Hint: Think
about what would happen if pea plants were allowed to cross-pollinate.)
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Virtual Lab
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Heredity
Introduct toGenetics
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Name ________________________________ Class _______ Date _________________
Part C: Flower Position
Reset the experiment setup but keep the pea plant as the model organism. This time,
select flower position as the trait to investigate. Once again, you will determine the
pattern of inheritance for this trait. This time, however, you will choose which
parental genotypes to cross and how to use the results to determine the pattern of
inheritance.
8. Use the space below to record the procedure and results of your experiment.
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9. How many offspring did you produce in each cross before you felt confident
enough to infer the pattern of inheritance based on your results? Explain your
reasoning.
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Virtual Lab
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Introduct toGenetics
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