Lecture 2 Bacteria And Viruses Flashcards

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1
Q

Why use bacteriophage in genetic study

A

Homosapiens 24 chromosome, drosophila 5 and bacteriophage only 1. No mito/chloro DNA / fast growth & repro/ easy to grow in lab & small workspace required. Natural DNA transfer mechanisms can be used to ‘map’ genes. Can be used to deliver DNA for experiments e.g. in cloning.

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2
Q

Nucleoid

A

Name given to bacterias one circular chromosome - bacteria may also have plasmids. Plasmid or nucleoid start to replicate at origin of replication (ori site) both strands separate and replicate in both directions eventually create 2 identical daughter plasmids w/one original and one new strand

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3
Q

Topoisomerase

A

Hoists ds DNA around it’s own axis forming supercoils and cutting it where needed. From relaxed to pos. Supercoil: adding two turns and over rotating or neg super cool: removing 2 turns underrotating

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4
Q

Growing bacteria in lab

A

Inoculate sterile medium w/ bacteria and allow to grow/ divide then use pipette to apply some to agar growth medium in Petri dish. Spread evenly w/glass rod and allow to incubate 1-2 days so bacteria form colonie

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5
Q

Selection medium - identify mutants

A

Grow bacteria on medium containing leu+ and leu- . Use a ‘handle’ to replica plate the colonies by transfer on the velvet surface (like a stamp.) Press onto new Petri plates one w. Leu+ & Leu - and one w/out Leu-. Mutant will not grow on medium w/out Leu- identify location of this colony by where it is missing on Petri w/out, collect colony from Petri w to culture for further study (Conclusion : colony that grows only on supplemented medium has mutant in gene encoding synthesis of an essential nutrient in this case Leu+)

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6
Q

Conjugation

A

Donor bacteria connects to recipient by cytoplasmic bridge. DNA replicates and transfers to recipient cell. Crossover in the recipient cell leads to formation of a recombinant chromosome.

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7
Q

Transformation

A

Ss DNA fragments taken up by a bacteria cell can exist as a plasmid or lead to crossover and recombination. When cell replicates and divides only one is transformed ( as only one of the parental strands has the recombination.)

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8
Q

Transduction

A

Bacteriophage injects DNA, replicates using bacterial DNA so bacterial DNA is broken down and incorporated into phage progeny then cell lyses (pops). Phage progeny infect new bacteria w/DNA forming recombinant chromosomes.

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9
Q

Cotransformation

A

DNA fragments close to one another on a genome more likely to be on the same fragment and recombined together so rate of cotransformation inversely proportional to distance between genes

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10
Q

Bacteriophage virus

A

Genetic materia (DNA or RNA) in a protein coat. Virulent phages reproduce by reproduction through the lytic cycle and always kill host by lysis (popping.) Temperate phages DNA integrates I to bacterial chromosome and can remain as inactive prophage by lysogeny process.

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