Assessment 5: Plasmids/Mechanisms of Genetic Exchange

three types of circular DNA replication mechanisms

-bidirectional (theta structure): 2 rep forks at one origin

-unidirectional (rolling circle): 1 rep fork from one origin

-special bidirectional (D-loop, mtDNA): 2 rep forks BUT sequentially

replication of e.coli genome

-one origin

-two replichores: CW (lagging strand) and CCW (leading strand)

-termination opposite the origin

five types of plasmids and their function

-F (Fertility) Plasmid

-R (resistance) Plasmid

-Bacteriocinogenic plasmid

-Ti Plasmids (Tumor inducing)

-Catabolic (dissimilation)

plasmid addiction system

Mechanism where bacteria ensure the survival of plasmid, which are small DNA molecules, by using a ‘post-segregational killing” system that eliminates cells and lose the plasmid

three mechanisms of gene transfer in bacteria

1. conjugation

2. transformation

3. Transduction

conjugation

direct transfer of genetic material from one bacterium to another through cell-to-cell contact

transformation

uptake of free DNA from the environment

Transduction

transfer of DNA from cell to cell via vector (bacteriophage) in nature

transformation vs. transfection

induce foreign genetic material into prokaryotic vs eukaryotic cells

bacterial gene map

-total time all genes took to enter recipient cell

interrupted mating technique

Stopping the process of bacterial conjugation at specific time intervals to determine the sequence in which genes are transferred from donor cell to a recipient cell

what is an episome (definition and actual examples)

-segment of extrachromosomal DNA that can exist in a cell in two states

• Fertility factor, Bacteriophage Lambda, Human Papillomavirus (HPV)

phenomenon of “diauxie”

sequential, two-stage growth observed when bacteria consume two different carbon sources, with an initial lag phase occurring btwn the consumption of the first and second source

how does Lac operon respond in terms of RNA Poly binding the promoter and repressor binding the operator

-lactose absent: repressor binds to operator

-lactose present: allolactose inactivates repressor

What are ONPG, IPTG, X-Gal

used in conjugation of enzyme beta-galactosidase

ONPG

B-gal enzyme cleaves it to produce yellow compound o-nitrophenol

IPTG

non-metabolize analog of lactose that acts as inducer for the lac and tac operons

X-Gal

chemogenic substrate that produces insoluble blue precipitate when cleaved by B-gal

eukaryotic vs prokaryotic firuses

euk: euk bacteria, cytoplasm, simple replication

prok: bacteria, nucleus of DNA virus or cytoplasm of RNA virus, more complex replication