Flashcards in Chapter 9: Genetics of Bacteria and Their Viruses Deck (48)
What is mobile DNA?
sequences that can be transferred between DNA molecules from one cell to another. This is a unique feature of bacterial genetic systems.
Do bacterial cells undergo meiosis?
no, they have haploid and diploid lifecycle stages
capable of synthesizing all of the necessary biochemical nutrients from simple inorganic nutrients.
can a prototrophic bacteria grow on MM?
yes, it can make everything it needs
a bacteria that requires one of more specific nutrients in order to survive. genetic defect is blocking the nutrient producing pathway
can an auxotrophic bacteria grow on MM?
no, it needs more nutrients. it can grow on MM if it is supplied with the stuff it cannot synthesize.
What is a carbon source mutant?
a mutant bacteria that cannot use a specific type of carbon source as energy. Ex, being able to grow in the presence of glucose, but not being able to grow in the presence of lactose (Lac-)
process of bacterial cells taking up DNA from their environment. begins with recipient cells uptake of a DNA fragment from the surrounding medium, and terminates with ONE strand of donor DNA replacing the homologous segment in the recipient DNA.
the ability for a cell to undergo transformation relies on the ____ of the cell.
If 2 markers can be transformed together, what does this indicate about their location?
they are very close together and can be taken up by the recipient DNA at the same time.
What is cotransformation?
when 2 genes simultaneously transform and enter the recipient cell. indicates that the 2 genes are close together if the occurrence of the 2 gene transformation is greater than the product of 2 single gene transformation occurrences.
The F+ factor is located in the ____ cell
if the fertility factor is integrated into the main bacterial chromosome of the recipient cell becomes an _____ cell
Hfr cell. high frequency of recombination.
What is an episome?
a genetic element that can exist free in the cell or as a segment of DNA integrated into the chromosome
If an F+ strain and an F- strain is mixed:
all cells become F+
If an Hfr strain and an F- strain is mixed,
Hfr cells go unchanged, and some F- cells will remain F-
What is conjugation?
the mating between an F- cell and an Hfr/F+ cell.
Does the pileus extend from the Hfr cell or the F- cell?
the Hfr/F+ cell/ the cell containing the fertility factor.
contact by the pileus forms the _____ bridge, here genetic transfer of DNA occurs
How does DNA replicate in a bacterial cell undergoing conjugation?
ROLLING CIRCLE REPLICATION.
Why is it possible that an F- cell that underwent conjugation will still remain F-?
DNA transfer begins within the fertility factors and drags some of the DONOR main bacterial chromosome genes with it. the F- cell might stay F- because not all of the F+ factor was transferred.
How does conjugation aid in recombination?
Genetic variation/crossing overof the donor cell is not possible because when the fertility factor was transferred from the donor to the f- cell, part of the donor's main bacterial chromosome was pulled along with it, and the transferred genes can thus undergo recombination with the recipient cell genes.
The Hfr strand transferes a _____ strand of DNA through the conjugation tube to the recipient cell
Outline the process of Hfr transfer.
1) Hfr cells contains bacterial chromosome with F+ factor, and the other cell is just an F- cell.
2) Hfr cell begins rolling circle replication
3) Hfr cell transfers a single strand of DNA, beginning of replication of transferred strand
4) conjugation tube breaks apart, and the original Hfr still has its original amount of DNA even though it transferred part of it, due to rolling circle replication.the F- cell copies the single strand it was given
5) recombination takes place between the Hfr donor fragment and the F- main bacterial chromosome.
6) if F is not transferred, or not integrated into the recipient main bacterial chromosome, the recipient remains F-
What is interrupted mating?
allows gene mating by deliberately interrupting DNA transfer during conjugation at different times.
What is the standard interruption mating pairs?
a prototrophic, antibiotic sensitive Hfr strain and an auxotrophic, antibiotic resistant F- strain.
How does the medium allow for interruption mating to determine gene mapping?
the medium that the conjugation pairs are plated on prevents the growth of the Hfr parents and only supports the growth of specific recombinants that can grow on streptomycin AND grow their own nutrients.
what is "time of entry"
time where no recombinants were detected.
T/F The number of recombinants in each curve of an interruption mating graph will increase with length of time of mating
true, they will eventually plateau though.