What is meant by the term genetic recombination?
Genes from a donor cell are transferred to the other participating, or recipient cell. The combining of genes (DNA) from two different cells.
How does it occur in prokaryotes if they do not perform meiosis?
By Vertical or Lateral gene transfer.
What is Veritcal Gene Transfer?
Genes pass from parents to offspring. Binary Fission.
What is Lateral Gene Transfer?
Genes are passed to other microbes of their same generation. i.e., Transformation, transduction, and conjugation.
A change in an organisms characteristics because of the transfer of genetic information. Transfers less than 1% of the cells DNA. Requires competence factor.
What is the first step of Transformation?
Naked DNA fragments from disintegrated cells in the area of a potential recipient cell are in the environment. The cell must be of the correct genus and be in a state of competence, which is a proper physiologic condition, to permit the entry of the DNA fragments to be integrated.
DNA that has been released from an organism, often after the cell is lysed, and the DNA is no longer incorporated into chromosomes or other structures.
What is the second step of Transformation?
The Naked DNA enters and integrates into the competent cells chromosomes.
What part of Transformation is rare?
The second step where Naked DNA needs to enter and integrate with the competent cells chromosomes. Less than 0.1% occurance.
What is an example of Transformation?
Griffith's experiment with pneumococcal infections in mice.
What is Griffith's Experiment with Pneumococcal Infections in Mice?
When S-type pneumococci (which produce smooth-appearing colonies, due to the presence of capsules) are injected into mice, the mice die of pneumonia. The mice survive when R-type pneumococci (which produce rough-appearing colonies, due to the lack of capsules) or heat killed S-type pneumococci are injected. But when a mixture of live R-type and heat killed S-type pneumococci-neither which is lethal by itself-is injected, the mice die, and live S-type organisms as well as R-types are recvered from the dead animals.
Why in Griffith's Experiment with Pneumococcal Infections in Mice did the mixture of live R-type and heat killed S-type pneumococci cause the mice to die?
The recombination of genes due to transformation from the genes of the heat killed S-type pneumococci to the live R-type pneumococci.
Method of transferring genetic material from one bacterium to another by way of a bacteriophage.
A virus that can infect bacteria.
What are the two types of Transduction?
Generalized and Specialized.
What happens in the Generalized type of Transduction?
Bacteriophage infection of a host bacterium injects intself and initiates the lytic cycle. The bacterial chromosome is broken into many fragments, any of which can be picked up and packaged along with phage DNA into new phage particles. When those particles are released and infect another bacterial cell, the new host acquires the genes that were brought along (transduced) from the previous bacterial host.
What happens in the Specialized type of Transduction?
Bacteriophage DNA always inserts itself into the bacterial host chromosome at a particular site. When the phage DNA replicates, it takes bacterial genes from either side of the site and packages them with its own DNA into new phages. Only genes adjacent to the insertion site, not genes from other parts of the host chromosome, are transduced. These genes can then be introduced into the phage's next host cell, where they will confer new genetic traits.
Why is Transduction significant?
It transfers genetic material from one bacterial cell to another and alters the genetic characteristics of the recipient cell. i.e., given the ability to metabolize a chemical. It incorporates phage DNA into a bacterial chromosome which demonstrates a close evolutionary relationship between the prophage and the host bacterial cell. The discovery that a prophage can exist in a cell for a long period of time suggests a similar possible mechanisms for the viral origin of cancer. Some animal viruses probably brought genes from previous hosts when they infected new human hosts. Provides a way to study gene linkage.
Genetic information is transferred from one bacterial cell to another that requires contact between donor and recipient cells, and transfers much larger quantities of DNA (occasionally whole chromsomes) using Plasmids.
What are the three different types of Conjugation?
Transfer of F plasmid, High Frequency Recombinations, and Transfer of F' Plasmids.
Small extrachromosomal DNA molecules.
Contain extrachromosomal DNA called F(fertility) plasmids. - Donor/Male Cells.
Lack F plasmids. - Recipient/Female Cells.
What do F+ cell create so conjugation can happen?
F pilus (sex pilus or conjugation pilus), a bridge by which it attaches to the F- cell when F+ and F- cells conjugate.
What happens when the F+ and F- cells conjugate?
A copy of the F plasmid is transferred from the F+ cell to the F- cell. Making the F- plasmid F+.
What is a Conjugation Bridge?
Mating channel where DNA is transferred as a single strand via conjugation.
How do HFR cells arise?
From F+ cells when their F plasmid is incorporated into a bacterial chromosome at on of several possible sites.
What is transferred during High Frequency Recombinations?
Segments of F plasmid and variable quantity of chromosomal DNA.
What is the product of High Freqency Recombination?
F- with variable quantitys of chromosomal DNA.
What is the recipient in HFR conjugation, F+ conjugation, and F' conjugation?
What is transfered during F' conjugation?
An F plasmid with a fragment of chromosomal DNA attached to it. = F' (F prime).
What is the product in F' conjugation?
F' cell with some duplicate gene pairs: one on chromosome and one on the plasmid.
What is Specialized Transduction?
Transduction that involves a bacteriophage where only genes near the prophage are transferred to another bacterium.
What is Generalized Transduction?
Transduction that involves a bacteriophage where fragments of host bacterial DNA of variable length and number are packed into the head of a virus.
R plasmids or R factors - much smaller than a bacterial chromosome. Can carry genes for resistance to various antibiotics and to inorganic toxic substances, sometimes used in disinfectants. Also includes genes needed for the plasmid to undergo conjugation.
What do Resistance Plasmids consist of?
Resistance transfer factor (RTF), and one or more Resistance (R) genes.
How can resistance plasmids be removed from a bacterium?
What are displacins?
Pieces of DNA isolated from soil bacteria and attached to usually harmless E.coli bacteria.
What do displacins do?
Move from the E. coli into the pathogens where they literally displace plasmids carrying harmful genes, leaving the former pathogenes now harmless.