- have resistance genes related to antibiotics and heavy metals that would kill ordinary bacteria. - R genes

- gene transfer by means of bacteriophages - can be generalized or specialized

Microbial genetics Flashcards by Sayara fazely

Resistance plasmids

have resistance genes related to antibiotics and heavy metals that would kill ordinary bacteria.
R genes

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Resistance bacteria are ______ through ____

passed from bacterium to bacterium through conjugation

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transfer of resistance plasmids occurs between

Occur between closely related genera

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exaple of closely related genera

Escherichia Klebsiella Salmonella Serratia, Shigella and Yersinia

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Vertical gene transfer

Gene transfer from mother to daughter cells

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horizontal/lateral gene transfer

gene transfer between unrelated cells

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Due to lateral gene transfer _____

organisms with similar genes may NOT have evolved from a common ancestor

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Prokaryotic reproduction ______ requires _____

never requires gene exchange

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Many euks reproduce ____ which requires ____

sexually, which requires meiosis and fusion of gametes

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Prokaryotes reproduce ____ by _____

asexually by binary fission or budding

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what makes a small amount of transferred DNA propagated?

if it integrates into a chrom or plasmid, or if it is a plasmid itself

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propagated

replicated and handed down to progeny cells

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euks are diploid or haploid

diploid

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proks are diploid or haploid

haploid

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because proks are haploid, what genes are expressed

recessive alleles or mutations are expressed in proks

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genetic exchange among euks is done by

gamete fusion

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Proks have 3 different mechanisms for gene exchange:

transformation
transduction
conjugation

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Transformation

gene transfer by taking up soluble DNA from the environment

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Conjugation, and what does it include?

Gene transfer that requires cell-cell contact
includes R plasmid, F plasmid, Hfr transfer

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Transduction

gene transfer by means of bacteriophages
can be generalized or specialized

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Griffith’s experiment, and the conclusion he found

an experiment with pneumococcal infections in mice
something from the dead S cells had “transformed” the R cells, making them smooth and virulent

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Transformation requires _____ cells, which ______

Competent cells which can take up DNA from the environment

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_______ transformations is ______

natural transformations is rare

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natural transformations is observed in

S.Pneumoniae, B.Subtillis and H.influenzae

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Artificial transformation

chemically competent cells

what are the 2 possible fates of linear DNA after entry in bacterial cell

- it can degrade in the cell cytoplasm - it can undergo homologous recombination and becomes part of the chromosome

RECA

if homologous sequence is present, RECA catalyzes it and lets recombination occur

how does the Linear DNA go into chromosome

Through the use of nucleases

plasmid DNA can exist ___

on its own as long as it has its own origin of replication

generalized transduction

any of the host bacterium's genes can be transferred

specialized transduction

only certain genes can be transferred

virulent phages

always replicate using the lytic cycle

temperate phages

can replicate using the lytic or the lysogenic cycle

lambda phages

can do lytic or lysogenic

all viruses can do ___ only some can do ____

lytic, lysogenic

Linear DNA must be _____

recombinated

only ____ cells can take in DNA, which is _____

confluent, random

an error in the assembly stage of phage replication causes

generalized transduction

an error in the prophage excision stage in the chromosome of phage replication causes

specialized transduction

lysogenic cycle exists

indefinetly (forever)

If specialized transduction occurs, _______ are always excised

same genes

gene exchange happens because of ______

mistakes done by bacterophages

Lederberg and Tatum discovered _____

conjugation

how was conjugation discovered?

Through mixing 2 different auxotrophs and recovered prototrophs

conjugation

requires cell-cell contact facilitated by sex pilli. Occurs in gram (-) bacteria

What gene does conjugation need

"tra" genes (transfer genes), this includes genes encoding proteins in sex pili

in gram (+) the mechanism for conjugation is ____

unknown

common types conjugation

F plasmic Hfr F' plasmid R plasmid Virulence plasmids

rolling circle replication

A single strand of the F plasmid enters the F-cell

OriT

marks the region on F plasmid that enters the recipient cell first - origin transfer

T/F A Hfr cell has the F plasmid integrated into the chrome

Hfr conjugation

Is genetically identical to F+ cell except its plasmid is not separate from the chromosome

the amount of DNA transferred in Hfr conjugation depends on ___

the amount of time the conj lasts

F+ cell and Hfr cell ....

can turn into or reverse back to each other

F' conjugation is

Begins with Hfr cell, F plasmid excides itself, but it doesn't do it percicley and takes some chromosomal genes with it, it is a mistake. - this makes it F'

F' plasmid

carries some chromosomal genes

genes on F' plasmif are transferred to reci[ient F-cell during ____

conjugation

R-plasmids

responsible for the transfer of antibiotic resistance genes - transferred like F-plasmids

What requires homologous recombination for the transferred genes to be inherited by progeny

Transformation, Hfr conj, generalized transduction

Mutation

any change in a cells DNA seq

small change in DNA

point mutations

Large change in DNA

deletions, insertions

mutations can be described by their ______

phenotypes

auxotrophic

defect in biosynthesis pathway so the mutant cell requires exogenous building blocks for growth

temperature sensitive

mutation that causes loss of a particular function at high or low temp

reversion (back mutation)

changes a mutated seq back to the original WT seq

Mutations can be induced by _____

mutagens

Transposon

mobile genetic seq that has genes for transposition - often has R genes - present in prok and euk

what can transpons do to DNA? what does this lead to?

they can randomly insert themselves into DNA, causing mutations and conferring antibiotic resistance

transposon mutagenesis

used to generate mutants for genetic studies

advantages of transposon mutagenesis

- mutations are marked by tn and antibiotic resist gene, the location of the must can be identified rapidly

disadvantaged of transposon mutagenesis

they only make insertion mutations, so mutations in essential genes may not be recovered

why would scientists do a genetic screen?

to discover genes involved in a process you're interested in

how to do genetic screen

1) determine pheno of mut 2)mutinogize 3) let mut grow in permissive conditions 4) replica grow in restrictive conditions, this identifies mut with wanted pehno

CRISPR-cas

protects prok from repeat viral infections

Microbial genetics Flashcards

(75 cards)