Virus that uses bacteria as its host.

They infect the host by injecting their DNA.

During reproduction, phages can be involved in genetic recombination called tranduction.

All mutations in bacteria and viruses are 

expressed directly because....

bacterium than can synthesize all essential organic compounds and can be grown on a minimal medium.

Minimal medium contains only an organic carbon 

source such as glucose or lactose  and a variety of ions

Auxotroph

Through mutation, this bacterium has lost the ability 

to synthesize one or more essential compounds; it must be provided to them in the medium in order to grow 

the transfer of genetic information between members of the same species.

Ex. Antibiotic Resistant genes

These cells contain a fertility factor that has the ability to donate part of their chromosome during conjugation.

One strand of the double helix moves into the recipient cell via the sex pilus and serves as a donor of genetic information.

High-frequency recombination 

Strain behaves as a donor and is a special class of F⁺cells.

This strain can donate genetic infomation to F^- cells,

but the recipient does not become F⁺

Hfr X F^- = High rate of recombination 

Horizontal Gene Transfer

the transfer of genetic information between members of related but distinct species.

Ex. Transfer of genetic information between members f related but distinct bacterial species. 

genetic information from one bacterium is transferred to another and it recombines with the second bacterium's DNA.

One strand of the double helix moves into the recipient cell via the sex pilus, and the other one remains. Both re-form their double helix and become F⁺.

 Fertility Factor (F factor)

An autonomous (independent) genetic unit also known as, plasmid.

Extrachromosomal heredity unit required for conjugation  

Facts

Only F⁺cells contain the fertility factor.

The fertility factor enables the F⁺cell to donate its plasmid.

Plasmid is mobile and consists of a circular, double-stranded 

DNA molecule containing 19 genes.

One strand of the double helix moves into the recipient cell via the sex pilus, and the other one remains. Both re-form their double helix and become F⁺.

The F⁺ cell becomes and Hfr cell when the plasmid/F factor

inserts a portion of it's self into the bacterial chromosome.

Since conjugation rarely lasts long enough for the entire chromosome to pass throught he conjugation tube, recipient cells mated with Hfr cells remain F^-. 

[image]

The position of the F factor determines

the initial point of transfer during conjugation between....

The Orientation of the F factor as it integrates. Genes adjacent to the F factor are transferred first, 

making the F factor the last part that can be transferred.

Conjugation occurs without hesitation. Each F^-cell involved with conjugation of an F⁺cell recieves a copy of the F factor, no genetic recombination occurs.

At a low frequency in a population of F⁺cells,

the F factor integrates spontaneously from

the cytoplasm to a random point in the baterial chromosome converting the F⁺cells to Hfr

When an F factor is excised (removed) from 

the chromosome of an Hfr strain and reverts to 

the F⁺state. The F factor is then referred to as F'

In this process the F factor often brings several adjoining genes with it.

In F⁺ x F^- matings the extremely low frequency 

of genetic recombination is caused by...

F⁺cells x F^- cells what happens to 

the recipient?

recipient becomes F⁺

low rate of recombination 

Recipient remains F^-

high rate of recombination

When an F' bacterium initiates conjugation

with an F^-cell.... (How a merozygote is formed)

The F factor is transferred to the F^-cell. As a result whatever chromosomal genes that are a 

part of the F factor are now present as duplicates in the recipient cell because the recipient still has a complete chromosome.

This process creates a partially diploid cell called a merozygote.

 A partially diploid cell resulting from the

transfer of an F' to an F^-cell.

Merozygotes are the only time

there is diploidy in bacteria.

Genetic recombination is a regulated process in

bacteria like eukaryotes.

Recombination in bacteria requires....

Functional gene products from RecA and RecBCD

Bacterial mutant cells that are dificient in

any of these components don't

undergo recombination 

A common form of recombination in many 

bacterial species.

When a double-stranded DNA enters a recipient, one 

strand is degraded, leaving the other strand as the only source of recombination. This strand must find its homologous region on the host chromosome, and once it does RecA facilitates (assists with) recombination. 

Resistance Transfer Factor 

(RTF)

Genes that confer resistance to antibiotics.

R-determinants are specific for resistance 

to one class of antibiotic. 

Several r-determinants present in a single plasmid 

will result in...

What happens if a bacterial cell contains r-determinant

plasmids but no RTF?

Encode for colicins that can kill neighbering bacteria.

Encodes an immunity proteinthat protects the host cell from toxin.

Col Plasmid is not usually transmissible to other cells.

Mechanism for recombining genetic 

information in some bacteria. Small pieces of extracellular DNA are taken up by a living bacterial cell and

are integrated stabily into the chromosome.

The entry of DNA into 

the host cell and recombination 

of the donor DNA

The recombinant region contains one host strand and one donor strand. These strands are from different sources and are not completely complementary, so the helical region is referred to as a heteroduplex. 

Genes that are close enough to be cotransformed are...

Phage T4

Explain the structure

[image]

DNA is contained within an icosahedral protein coat  which makes up the head of the virus.

The head is connected to the tail, with binding sites recognizing the E.coli cell wall(E.coli= bacterial host).

Life Cycle of phage T4

1)Initiated when the virus binds by adsorption (adhesion) to the bacterial host cell.

2)The tail contracts, the central core penetrates the cell wall and the DNA moves into the cytoplasm of the host (host=bacteria)

Bacterial DNA, RNA and protein synthesis is inhibited.

3)Host DNA degradation is initiated.

4)Components of the head, tail and tail fibers are synthesized.

5)When approximately 200 new viruses have been constructed, the bacterial cell is ruptured by the enzyme lysozyme and phages are released from the host cell.