Chapter 6 Conjugation Flashcards
Bacteria are useful genetic models because:
_______: fewer genes and fewer bases than other organisms
_______: mutations can be observed directly because there is one copy of each gene
_______: can be measured in minutes
_______: allow detection of rare events
_______: bacterial culture is easy and inexpensive and takes up very little space
_______: mutants are easily created, identified, isolated, and manipulated for study
1) genome simplicity
2) haploid genomes
3) short generation times
4) enormous # of progeny
5) ease of propagation
6) heritable differences
Bacteria genomes are usually composed of a _______, which carries mostly essential genes
single chromosome
The _______ is usually covalently closed, circular molecule of double-stranded DNA
Bacterial Chromosome
_______: small double-stranded circular DNA molecules containing nonessential genes in bacteria
plasmids
An _______ plasmid carries antibiotic resistance genes that can be transferred to recipient cells
R (resistance)
The ________ plasmid contains genes that promote its own transfer from donors to recipients
F (fertility)
_______ plasmids can replicate independently of the bacterial chromosome so that the number of plasmids per cell can increase rapidly
high-copy-number plasmids
_______ plasmids are present in one or two copies per bacterial cell and usually cannot replicate independently of the bacterial chromosome
low-copy-number plasmids
What are the 3 types of recombination in prokaryotes?
- Each method involves ________ transfer of genetic material from a donor cell to a recipient cell
1) conjugation
2) transformation
3) transduction
- One-way
_______ is the transfer of replicated DNA from a donor to a recipient
conjugation
_______ is the uptake of DNA from the environment
Transformation
_______ is the transfer of DNA from one bacterium to another by a viral vector
transduction
genetic information is transferred through a hollow tube, called a _______
conjugation pilus
Donor cells possess an F factor and are called _______
F+ cells
Recipients lack an F factor and are called _______
F- cells
A bacterial strain containing ampR _______ grow on ampicilin
will
A bacterial strain containing ampS _______ grow on ampicilin
won’t
After conjugation, the recipient cell is called the _______ cell
exconjugate
Describe the mechanism for Conjugation I (4)
1) Conjugation pilus forms
2) Gene expression produces relaxosome
3) Relaxosome cleaves 1 bond on the T strand
4) Relaxosome degrades leaving relaxase on 5’ end of T strand
Describe the mechanism for Conjugation II (3)
1) relaxase facilitates T strand through conjugation pilus
2) rolling circle replication begins at Ori-T of donor cell
3) recipient cell uses transferred DNA as template for replication
A large component of the F factor consists of 4 _______ elements
insertion sequence
IS elements are mobile segments of bacterial DNA that can _______ themselves to new locations
transpose
Circular elements, like the F factor, can integrate into the bacterial chromosome to form an _______
episome
When the formation of an episome occurs with an F factor, the cell is called a _______ cell
Hfr (high frequency recombination)
In Hfr gene transfer, the complete transfer of the bacterial chromosome is not accomplished leading to a _______ fragment
double-stranded LINEAR
After conjugation of the partial T strand, homologous _______ occurs between transferred DNA and circular chromosome recipient
- then the transferred strand gets _______
recombination
degraded
Donor cells carrying F’ factor are called
F’ cells
An F’ donor bacterium contains a functional F factor derived from _______ excision of the F factor from an Hfr Chromosome
aberrant (imperfect)
exconjugants that contain complete F’ factor are called _______ because they contain 2 copies of the bacterial chromosome genes found on the F’ factor
partial diploids
_______ = a state when a partially diploid bacterial cell is produced
merozygote
