Download 03/26/2017 Worksheet - Iowa State University

Chromosome number
alteration and prokaryotic
gene transfer.
Supplemental Instruction
Iowa State University
Leader: Matt C.
Course: Biol/Gen 313
Instructor: Dr. Myers & Dr. Vollbrecht
Date: 03/26/2017
Introduction: This worksheet discusses material covered in the twenty-fourth and twenty-fifth
lectures (03/10/2017 and 03/20/2017). Chapters 6 and 7 examine these topics.
Concepts
1. Aneuploidy and polyploidy.
2. Introduction to prokaryotic gene transfer.
3. High-frequency recombination.
Material
1. Aneuploidy and polyploidy.
In this section, we’ll examine aneuploidy and polyploidy.
1. What is the difference between aneuploidy and polyploidy? Which is more likely to
be stable?
2. Determine if the following scenarios are examples of aneuploidy or polyploidy and if
so, decide which.
a. Trisomy 21.
b. Turner Syndrome.
c. Human female cells with Barr bodies (inactivated X chromosomes).
d. Klinefelter Syndrome.
e. A sample of human smooth muscle arterial wall cells exhibit twice the normal
nuclear DNA amount.
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3. What can polyploidy be useful for? What type of polyploidy does this helpful form
usually take? How does this arise in broad terms?
2. Introduction to prokaryotic gene transfer.
In this section, we’ll examine the broader strokes of horizontal gene transfer in
prokaryotes.
1. There are three methods of horizontal gene transfer. What are these?
2. Describe the contact-dependent form of horizontal gene transfer. What is the factor
that a bacterial cell needs to complete this? What does the factor code for?
3. In the following scenarios, determine if conjugation can occur.
a. An F+ cell with an F- cell.
b. An F+ cell with another F+ cell.
c. An F+ cell with an F- cell with a filter in the way (like the U-tube experiment).
d. An F+ E. coli with an F- S. enterica.
4. Explain what happens during bacterial transformation.
5. Explain how viral-mediated horizontal gene transfer occurs.
3. High-frequency recombination.
Here, we will focus on Hfr mostly as it relates to gene mapping.
1. When is a bacterial cell be considered Hfr? What term is used to describe F factors
that can make Hfr cells?
2. A bacterial chromosome is known to have genes G, H, I, J, and K which are involved
in metabolizing certain substrates. You isolate two Hfr strains with F factors
integrated at different sites. You use an interrupted mating test between the Hfr strain
and an F- strain and note when growth of formerly F- cells occurs on minimal media
plates after a determined amount of time in which mating was allowed. From this,
you compile a chart listing the time at which 50% of the formerly F- cells appeared to
uptake each of the genes described above.
Sample
1
Sample
2
G
3 min
G
4 min
H
1 min
H
6 min
I
3 min
I
5 min
J
8 min
J
7 min
K
5 min
K
2 min
a. Which cells are auxotrophic? Which are prototrophic?
b. Draw the chromosome of the bacterium used in this experiment with the relative
locations of the genes described and where the F factors likely integrated.
4. Performing a similar experiment to the above, but with genes M, N, O, and P, you collect
the following data in graphical form.
a. Draw the chromosome of the bacterium used in this experiment with the relative
locations of the genes described and where the F factors likely integrated.
Things to do next
 Focus your review on things that were difficult from this worksheet. If it was really
challenging, don’t worry; these are meant to be tough and push your understanding of the
topics we covered.
 The Hfr material is the most interpretive of these topics. The other material should be
mostly definition-based, so memorizing that material with flashcards or another preferred
method is a good idea.
 If you have any questions, ask me in session, in class, or by email. I’m more than happy
to help.
 Next session will be on Tuesday (03/28/2017) from 7:10 to 8:00 PM in Gilman 2109. We
will be covering the new material that we’ll talk about in lecture on Monday.