Genetics - Chapter 5 [Part II]

Zygotic induction

When a bacterial cell becomes infected through conjugation rather than transduction.

Abbortive transduction

When a phage injects new bacterial DNA into a host but incorporation never occurs. This happens when recombination doesn't. Recal that linear DNA will be destroyed unless incorporated.

lytic pathway

When a virus injects genetic information into a bacteria causing it to lyse after continuous protein development. This is the only option for virulent bacteria. Temperate phages may enter this pathway occasionally.

Why does transduction allow mixing of bacterial DNA?

When a virus is accidentally packed with some bacterial DNA in addition to the viral genome, new bacterial information may be transfered.

What happens to phage DNA after injection into a host cell

Incorporation into host genome

What happens if a temperate phage is injected into a cell which isn't growing?

Lysogenic cycle

Bacterial lysogen

A bacterial cell in the lysogenic cycle. It carries phage DNA but isn't at immediate risk of bursting. A "carrier"

transductant

A bacterial cell which has received DNA via transduction.

abnormal outlooping

A failure in the outlooping process which results in excision at locations other than the intended attachment sites. The result may be uptake of a bacterial marker.

lambda phage [where does it bind?]

A model e. coli bacteriophage for special transduction. It always binds between gal and bio sites and may accidentally take one (but not both) of them with it during excision.

prophage

A prophage is a phage (viral) genome inserted and integrated into the circular bacterial DNA chromosome or existing as an extrachromosomal plasmid. This is a latent form of a bacteriophage, in which the viral genes are present in the bacterium without causing disruption of the bacterial cell.

What kind of information might accidentally be transfered by a prohead?

A small amount of DNA, usually a single gene. That's all there's space for. So when we say a phage is B+ that might literally be the only genetic attribute it has.

proheads

A viral capsule created inside a host cell. They suck up viral DNA to transfer into the new host cell. Accidental uptake of host DNA leads to transduction

Can a prophage become virulent?

Almost all prophages will eventually activate, lysing the cell to release their content.

phage recombinance

If enough phage are bound to a bacterial cell, some of the injected genes might be different and result in mixing.

What happens if a temperate phage is injected into a cell which is growing?

Lytic cycle

What happens during zygotic induction if the recipient is a lysogen?

No lysis occurs because of the repression factors.

During transduction which kinds of genes can be taken up by the phage DNA?

Only those immediately on either side of the attachment site can be taken in. The phage DNA simply isnt large enough to carry multiple genes, and there's no mechanism for the uptake of genes on any other location.

What does high cotransduction frequency imply?

Since transduction can only transfer small segments of DNA, frequent cotransduction implies two markers are closely-linked.

specialized transduction

Specialized transduction is the process by which a restricted set of bacterial genes are transferred to another bacterium. Specialized transduction occurs when the prophage excises imprecisely from the chromosome so that bacterial genes lying adjacent to the prophage are included in the excised DNA. This process can only lead to transduction of genes immediately on either side of an attachment site.

lysogenic pathway

The dormant growth pathway for viral infection. Temperate phages can enter this pathway *or* the lytic pathway. Virulent phage cannot enter this pathway.

normal outlooping

The process by which phage DNA excises itself from a bacterial chromosome. The DNA bends until a tight loop forms. Then, excision occurs and both pieces reseal

A bacterial cell is held in lysogenic stage by a phage. Conditions improve for growth, but no DNA damage occurs. What results when another phage binds?

The second phage injects its information but is repressed. Because of the repression factors being synthesized by the initial phage, the cell is said to be immune to further infection

Relationship between genetic and physical maps

They have consistent order, but suffer from different proportions. What appear as large gaps on one map may appear very proximate on another. This occurs because large number of DS-break sites "increase the distance" on the genetic map.

A lysogen conjugates with a sibling and exchanges DNA. After twelve minutes of transfer, the recepient dies. What happened?

Twelve minutes from the origin of transfer site was a segement of prophage DNA.

What type of damage might cause a lysogenic virus population to enter the lytic pathway?

UV light damage. The cell is going to die so the virus decides to find a better host cell.

transduction

Viral transfer of genetic information. Like all DNA exchange in bacteria it has a "sender" and "receiver" and is one-way.

Can a virulent phage become a prophage?

Virulent cells immediately burst a bacterial cell. Thus they can not enter the dormant prophage state since their host has been killed.

Will transduction occur in a U-tube with filter?

Yes, since the phage are incredibly tiny.