Download Genetics

Virtual Biology Laboratory
Student:
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Date:
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Module:
Genetics
Exercise I: Phenotypes
No worksheet is needed for this exercise.
Exercise II: Chromatography
Part A:
Using Thin Layer Chromatography to Separate the Components of a Mixture
Be sure to calibrate the Rf ruler as per the instructions in the Options section.
Drag and drop the extracts from the uppermost family of glyptodonts (the white
box next to the picture) into the blue box at the base of the chromatography
apparatus. Press Start.
When the solvent front has traveled an appropriate distance, click Stop. Then
having calibrated the Rf ruler, note the number of pigments detected in the two
extracts, their color, and their Rf value. The Rf value can be determined by
dragging the purple ruler down until the purple line is aligned with the middle of
the molecule of interest. Repeat for the other three pairs of glyptodonts.
Genotypes of
Parents
Number of
Pigments
Color(s)
Rf value(s)approximate
Aa X Aa
Aa X aa
AA X aa
aa X aa
1. How many pigments were detected in each sample? ____________
2. Are the pigments the same in each sample?
______ Yes
_______
No
3. What is the color and Rf of each pigment molecule detected?
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4. How do the colors and Rf values of the pigments correlate to the shell
colors of the glyptodonts?
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Exercise III: Electrophoresis
Load the Standard Molecular Weight Marker (ST ) by dragging it from the sample
panel to the right of gel apparatus and placing it into one of the four wells at the
top of the gel. Load one or more protein samples extracted from organisms with
known genotypes by dragging the appropriate box (AA, Aa, aa) from the panel to
the right and placing it into one of the remaining wells.
Click the Start button on the PowerPac power supply. When the visible marker
on the right hand side of the gel holder gets near the bottom of the gel, click the
Stop button.
Now click Stain. When staining is complete, all proteins will stained various
shades of blue. By comparing proteins detected in your extracts with proteins of
know molecular mass in your standard, the size of approximate size of the
unknown proteins can be determined. Make special note of the approximate
weight of any proteins that appear to be found in one sample but not another.
You may sketch the results of your electrophoresis experiment using the diagram
below.
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Is the presence or absence of a particular protein(s) correlated with the presence
of absence of a particular allele(s)?
______ Yes
_______
No
Since genes are expressed by coding for the production of individual proteins, do
any proteins found appear to be under the control of any particular allele(s)?
______ Yes
_______
No
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What can you conclude about the relationship of specific proteins to the presence
or absence of specific alleles?
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Exercise IV: Genotypes
Start a problem by clicking the New button. You will be presented with
phenotypes for the parents (P1a and P1b) and offspring (F1) for the first mating
between the parents. If you think you know the genotypes of the parents, select
the appropriate genotypes for both parents from the choices on the pull-down
menus located in the boxes to the right of P1a= and P1b=.
If you cannot make a reasonable choice, you will have to perform a second
mating. To initiate the F2 mating, select and drag any two individuals from the
P1a, P1b, or F1 (parents or offspring) into P2a and P2b.
When both P2 parents are in place, you will be presented with the phenotypes
for the F2 offspring. Additional F2 matings may be performed by clicking the
Reset F2 button.
Based on the results of your mating experiments, you should be able to answer
the following questions and explain why your answer is correct.
1. AA X AA: Are both parents "true breeding" for shell color? That is, will the
dominant phenotype be found in all of the offspring?
______ Yes
_______
No
2. Aa X Aa: In the offspring from this cross, 75% are red and 25% are yellow.
Is this what you would predict?
______ Yes
_______
No
3. AA X Aa: The probability of getting a yellow shelled glyptodont from this
mating is 0%.
______ True
_______ False
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4. aa X aa: This is the only cross that ensures all yellow shelled offspring.
______ True
_______ False
5. A? X aa: This type of cross is the ONLY way to determine the genotype of
the first parent.
______ True
_______ False
6. Does shell color appear to be under the control of a single gene with two
alleles, where the dominant phenotype is red and the recessive is yellow?
______ Yes
_______ No
7. After the results of your chromatography and electrophoresis experiments,
can you reasonably conclude that the red shell color is produced by a
single red pigment whose synthesis is catalyzed by an enzyme
(approximate mass of 45 kd) coded for by the dominate allele?
______ Yes
_______ No
Copyright ©2003 Wadsworth, a division of Thomson Learning, Inc. Thomson Learning is a trademark used
herein under license.