MCB 229 Spring 2000 Study Guide 15 Prof. Terry
Covers Lecture for April 4
This study guide is intended for you to use while you are
doing the assigned text reading. Quiz questions will be made with reference to
topics in this study guide. Quiz #15, based on questions from this study guide,
must be completed by midnight before the class on Tuesday, April 4. You will
need to create your "myWebCT" account and visit the MCB 229 WebCT page in order
to access this quiz.
Chapter 14. Microbial genetics: recombination and
plasmids.
- What is general recombination? What DNA and proteins are required?
- What is nonreciprocal general recombination? How does it differ from
general recombination? (Hint: compare figs. 14.2 and 14.3).
- What is
site-specific recombination? In what context is this likely to occur?
- Are
there any recombination processes that do not require homology?
Explain.
- What is the difference between vertical and horizontal gene
transfer?
- What do the terms exogenote, an endogenote, and merozygote
describe? When a linear fragment of DNA that contains some regions homologous to
the host chromosome is brought into a cell, what possible fates can befall it?
- We've looked at plasmids before, but they are so important that we should
review their properties here. What is meant by each of the following
terms?
- multiple copy plasmid
- single copy plasmid
- replicon
- episome
- copy number
- “curing” a plasmid
- incompatible plasmids
- virulence plasmids
- metabolic plasmids
- plasmid toxin
- Col plasmid
- bacteriocin
- R factor
- F factor
- conjugative plasmid
- pilus
- rolling circle replication
- Almost all bacterial cells isolated from nature contain one or more
plasmids. In laboratory culture plasmids are frequently lost. Are plasmids
necessary? Explain.
- How might you demonstrate the presence of a plasmid in a
bacterial cell?
- What is a transposon? What is an insertion sequence (IS)? Do
all transposons have IS? Are enzymes responsible for transposition? If so, where
are the genes for them located? Do transposons carry other genes?
- Compare
and contrast plasmids and transposons. How are they similar? How are they
different? How are they related?
- When you have completed the rest of the
chapter, be sure you can recognize the differences between transformation,
conjugation, and transduction. These are the three mechanisms for gene transfer
in bacteria. The remaining questions in this study guide focus on these
mechanisms.
- What is bacterial conjugation? Does it require physical
contact between bacteria? What is meant by the terms F+,
F-, Hfr, sex pilus?
- During Hfr conjugation, what determines the
origin of gene transfer? For a given Hfr strain, is this order always
predictable? Is it efficient? Is there a limit to the amount of DNA that can be
transferred?
- What is an F' plasmid? Is it more similar to an F+,
Hfr, or F- state?
- What is transformation? How efficient is it?
What is meant by "competence"? Under what conditions do cells become naturally
competent? Can cells that do not possess transformation machinery be
transformed? If so, how? Is there a limit to the amount of DNA that can be
transferred?
- What is transduction? What does it accomplish? Is there a limit
to the amount of DNA that can be transferred?
- For now, skip the discussion
of lysogeny, temperate phages, and prophages. We'll devote some time to this
when we study viruses.
- In general terms, what is the difference between
generalized and specialized transduction?
- Until the advent of powerful gene
sequencing technology in the past decade, the organization of bacterial genomes
was studied mainly by conjugation and transduction studies. The single most
important experiment was an interrupted mating experiment (see Fig.
14.22). Data such as the graph in Fig. 14.22(b) is used to create maps such as
those in Fig. 14.23 (also shown in tabular form in Table 14.4). Examine these
figures, with accompanying text, to get a sense of how these techniques work.
- Look at the genetic map in Fig. 14.23. What is the relationship of this map
to the bacterial DNA? How was this map constructed? What to the numbers 0, 10,
20, etc. refer to? Why does the map end at 100?
- Locate the genes “lac
A,Y,Z,O,P”, “argR”, “his G,D,C,B,H,A,F,I,E”, and
“argS”. When would they be transferred in a conjugation experiment,
relative to “purB”? Why do some genes have multiple letters, while
other genes only have a single letter? (Hint: remember operons).