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Name: ________________________
Teacher’s Name: ________________
Class: ________________________
Date: ________________________
TITLE
How To Use This Lab Skeleton:
The instructions are in ORANGE.
The content is in BLACK. Take out the
orange and type in your responses in
black. You are finished when no
ORANGE remains!
(change this to an original title that sums up the lab)
Introduction:
In the mid-1800s an Austrian monk named Gregor Mendel studied the
heredity of pea plants. His observations and conclusions formed the foundation
for the modern day study of genetics. Many of the principles he discovered in his
test organism (the pea plant) are evident in other organisms.
In this experiment, the test organism will be corn. The benefit of using this
organism is its prolific reproduction. One kernel of corn planted in the earth can
yield a plant with many corn flowers. These flowers can self-fertilize or be crossfertilized. The flowers in this experiment were cross-fertilized. The flowers then
became a corn cob. In the same way that the pea pod produces many peas (seeds),
the corn cob produces hundreds of kernels (seeds). Therefore the kernels that
are seen on the cob are the offspring of two parents.
In this lab, you are given a cob of corn, and asked to collect observations that
will determine the genotype of the parents. The trait being studied is seed color,
and the two phenotypes are purple and white.
Quickly glance a the ear of corn. Then hypothesize both the ratio of purple
kernels to white kernels and hypothesize the genotype of the two parents who
made this specimen.
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PURPOSE: The purpose is the reason why the lab is being done. You type the
purpose of the lab (in your own words) here.
HYPOTHESIS: You type your hypothesis here. A hypothesis is a testable
statement about what you think is going to happen when the experiment is
performed. It should include both a guess AND a reason why you think that guess
is correct.
MATERIALS:
You add a list of what you used.
PROCEDURE:
1. Place a rubber band around a specimen of corn cob so that it bisects the ear
lengthwise. The rubber band divides the ear of corn into two sides and
makes counting the kernels easier.
2. Count the kernels that have the same phenotype on one half of the ear. Be
sure to count EVERY kernel.
3. Record the number of kernels with that phenotype on the data table.
4. Count the kernels with that phenotype on the other side of the ear of corn.
Be sure to count EVERY kernel.
5. Record the number of kernels with that phenotype on the data table.
6. Repeat steps 2-5 for the second phenotype.
7. Calculate the ratio of one phenotype to another. Round to the hundreths.
DATA: Neatly type your data below. Be sure that EVERY number has a unit and
the correct number of significant figures is used for all calculations.
Phenotype
Side 1
Side 2
Total
Ratio
Purple
White
1. If the total number of both phenotypes were different from one another:
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a. The kernels with the dominant color inherited a dominant allele. This
allele can be represented by any letter of the alphabet, written as a
capital, but typically the first letter of the dominant phenotype will
be used. Write the dominant allele here:
____________________________________________________
____.
b. The kernels with the less frequent color inherited two copies of a
recessive allele. This allele must be represented by the same letter
as the dominant allele, only now is written in lower case. Write the
recessive allele here
____________________________________________________
___.
c. Each kernel inherited one allele from each parent (one from the
sperm, or pollen, and one from the egg). There are three possible
combinations of alleles. Write them here:
______________________
__________________________________.
d. Write the three possible phenotypes for each combination of alleles:
Genotype
Phenotype
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e. Write the genotypes in the Punnet Square boxes below in the ratio in
which you determined from your data. Start with the recessive
phenotype. (For example, if you got a 3:1 ratio of purple to white,
white is recessive and the genotype for white should be written in 1
box out of the four boxes below). Determine the other genotypes and
the parents.
For a visual representation, you will always want to graph your data. Pay attention
to where the independent and dependent variables go. You can make a computergenerated graph, or you can print the graph grid below and hand-draw your graph
(use colored pencils to make it look really nice). For this experiment, you should
construct a histogram with your hypothesized ratio and your experimental ratio.
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Figure 1: Title (look back in your “How To Make A Graph” notes to see how to write a
good title for a graph)
LEGEND
Remember to
label your axes!
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CONCLUSION:
Use your answers to the following Analysis Questions (which you worked out on
your Rough Copy) to construct a conclusion paragraph. YOU SHOULD NOT SHOW
THE QUESTIONS IN YOUR FINAL DRAFT! Your interesting and well-written
paragraph should contain the answers to all of the questions below. Remember to
use scientific writing (passive voice, no personal pronouns).
1.
Was your hypothesis supported or rejected? Explain.
2. What is the definition of a dominant allele? Were either of the alleles whose phenotypes
you observed found to be dominant?
3. What is the definition of a recessive allele? Were either of the alleles whose phenotypes
you observed found to be recessive?
4. Was the ratio EXACTLY the same as the predicted ratio? If not, explain why the ratio is
not exactly the same.
5. What was the genotype of the parents of this ear of corn?
6. Suggest an improvement or follow-up experiment for this lab (you MUST make a
suggestion!).
After you have finished writing the Conclusion, go back and write the Title. The
Title should be a short statement that sums up what the entire lab was about. Be
creative – but make sure the title represents the experiment! You cannot use the
title that your instructor used!
Last-minute check! Did you use the spellchecking feature to make sure your words
are spelled correctly? Have you removed ALL of the instructions from the lab
skeleton? Are you going to make sure your lab report prints neatly (do not cut the
data section or the graphs across two sheets of paper!) and is stapled in the upperleft hand corner?