Module 8 Lec 2 Flashcards
What is natural transformation in bacteria?
Natural transformation occurs when a recipient cell has the enzymatic machinery to import DNA from its environment.
What is artificial transformation in bacteria?
Artificial transformation involves damaging the recipient cell walls, allowing donor DNA to enter the cell.
How are cells made competent for transformation?
Cells are made competent by treating them with calcium at cold temperatures, which increases their ability to take up DNA.
What is electroporation in bacterial transformation?
electroporation is the process of mixing donor DNA with recipient bacteria and subjecting them to a brief high-voltage shock, which opens up the cell membrane to allow DNA uptake.
What is the result of conjugation between an F+ and F- cell?
After conjugation, the F- cell becomes F+ and can now act as a donor in future conjugations.
How does the F-plasmid facilitate conjugation?
The F-plasmid codes for a pilus (a tube-like structure) that allows the F+ cell to connect with the F- cell and transfer the plasmid DNA.
What happens when an F+ bacterium conjugates with an F- bacterium?
During conjugation, the F+ cell transfers a copy of the F-plasmid to the F- cell, turning it into an F+ cell.
What is the F-plasmid in bacterial conjugation?
The F-plasmid (fertility plasmid) carries genes that allow a donor bacterium (F+) to transfer DNA to a recipient (F-) during conjugation.
What is conjugation in bacteria?
Conjugation is the transfer of genetic material between two bacterial cells through direct contact, typically involving a pilus.
What does Hfr stand for in bacterial conjugation?
Hfr stands for High Frequency Recombinants, which are bacterial cells with the F-plasmid integrated into their chromosome.
What happens when an Hfr cell conjugates with an F- cell
During conjugation, the Hfr cell transfers part of its chromosomal DNA (including the F-plasmid) to the F- cell. However, the full F-plasmid is rarely transferred.
How is an Hfr different from an F+ cell?
An Hfr cell has the F-plasmid integrated into its chromosome, while an F+ cell carries the F-plasmid as an independent plasmid.
What is a key feature of Hfr conjugation?
In Hfr conjugation, the chromosomal DNA is transferred along with the F-plasmid, but usually not all of it. This results in genetic recombination in the recipient cell.
Can an F- cell become an F+ cell by conjugating with an Hfr cell?
No, because Hfr conjugation typically does not transfer the full F-plasmid to the F- cell, so the F- cell does not become F+.
What is the basic process of conjugation involving Hfr?
Hfr conjugation involves the transfer of chromosomal DNA from an Hfr cell (a bacterium with the F-plasmid integrated into its chromosome) to an F- cell (a bacterium lacking the F-plasmid).
How does the Hfr cell transfer its DNA during conjugation?
The Hfr cell forms a pilus and transfers a portion of its chromosomal DNA into the F- cell. The DNA is transferred starting at the integration site of the F-plasmid in the chromosome
Why is the F- cell not converted into an F+ cell after Hfr conjugation?
The F- cell typically does not receive the entire F-plasmid during Hfr conjugation, just part of the chromosomal DNA. Without the full F-plasmid, it does not become F+.
What happens to the Hfr cell’s chromosome during conjugation?
The Hfr cell’s chromosome undergoes rolling-circle replication as the chromosomal DNA is transferred to the F- cell. A copy of the transferred DNA is synthesized in the F- cell as well.
Can Hfr conjugation lead to recombination in the F- cell?
Yes, the transferred chromosomal DNA can recombine with the F- cell’s chromosome, leading to genetic recombination.
What is the outcome for the recipient F- cell in Hfr conjugation?
The F- cell may incorporate part of the Hfr cell’s chromosomal DNA into its own genome, but it does not gain the F-plasmid and therefore remains F-.
Why are Hfr conjugations used to map bacterial genes?
Hfr conjugations can be used to map genes based on the order in which chromosomal DNA is transferred to the F- cell, allowing researchers to determine gene linkage and gene distances.
What is an F’ plasmid?
An F’ plasmid is an F plasmid that contains a portion of chromosomal DNA that was accidentally excised from an Hfr cell along with the F plasmid.
How does an F’ plasmid form?
It forms when an Hfr plasmid excises imprecisely, taking chromosomal DNA with it.
What happens when an F’ plasmid is transferred?
The recipient becomes F+ and receives both the F plasmid and chromosomal genes.
How is F’ plasmid transfer different from Hfr?
F’ transfers both plasmid and chromosomal DNA, while Hfr mainly transfers chromosomal DNA
What is the result of F’ plasmid transfer
The recipient gains F+ status and may experience gene duplication.
What happens to chromosomal genes on the F’ plasmid?
They can recombine with the recipient’s chromosome.
What happens during F plasmid transfer in conjugation?
The F plasmid is transferred from the F+ (donor) cell to the F- (recipient) cell via a sex pilus, converting the recipient to F+.
What does F+ to F- conjugation result in?
F+ cell transfers its F plasmid to an F- cell, making the recipient F+ and capable of future conjugation.
What is a partial diploid in F’ plasmid conjugation?
A partial diploid results when an F’ plasmid carries a fragment of the host chromosome, giving the recipient two copies of some genes.
How is an F’ plasmid different from an F plasmid
An F’ plasmid contains chromosomal genes in addition to the usual F plasmid genes, which can be transferred to a recipient cell during conjugation.
How does Neisseria gonorrhoeae become resistant to penicillin?
Through a plasmid-derived gene from Haemophilus influenzae, which produces penicillinase, an enzyme that breaks down the beta-lactam ring of penicillin.
What is the role of penicillinase in penicillin resistance?
Penicillinase destroys the beta-lactam ring in penicillin, making the antibiotic ineffective against Neisseria gonorrhoeae.
