chapter 7: genetic transfer and mapping in prokaryotes

strains, haploid, loss, eukaryotes, 1

• like eukaryotes, bacteria often possess allelic differences that affect their cellular traits

  • however, these allelic differences (such as different sensitivity to antibiotics) are between different …. of bacteria because bacteria are usually ….

  • this fact makes it easier to identify … of function mutations in bacteria than in …..

    • usually only have … copy

genetic transfer, dna, one

researchers rely on a similar phenomenon called … ….

in this process, a segment of bacterial … is transferred from …. bacterium to another

diversity, conjugation, direct physical, transduction, viruses, transformation, uptake, environment

• 3 ways to transfer genetic material in prokaryotes

  • like sexual reproduction in eukaryotes, genetic transfer in bacteria enhances genetic ….

  • transfer of genetic material from one bacterium to another can occur in 3 ways:

    • …..

      • involves … …. contact

    • …

      • involves ….

    • ….

      • involves … from the …..

donor, recipient, strand

direct contact: requires direct contact between a … and a … cell

the donor cell transfers a … of dna to the recipient

fragment, chromosomal, newly, recipient, dna, chromosome

transduction (virus): when a virus infects a donor cell, it incorporates a …. of bacterial …. dna into a … made virus particle

the virus then transfers this fragment of dna to a …. cell, which incorporates the … into its ….

dies, environment, recipient, dna, chromosome

(transformation): when a bacterial cell …., it releases a fragment of its dna into the ……

this dna fragment is taken up by a … cell, which incorporates the ….. into its …..

lederburg, tatum

genetic transfer in bacteria was discovered in 1946 by joshua …. and edward ….

nutritional growth, auxotrophs, needed, prototrophs, basic, environment

• lederberg and tatum were studying strains of E. coli that had different … … requirements

  • …. cannot synthesize a … nutrient

  • …. make all their nutrients from …. components in the …..

biotin, methionine, leucine, threonine

• one strain was designated met- bio- thr+ leu+ thi+

  • it required one vitamin (….) and one amino acid (…)

  • it could produce the amino acids …. and ….

thiamine, leucine, threonine

• another strain was designated met+ bio+ thr- leu- thi-

  • had the opposite requirements for growth

  • it required one vitamin (…) and 2 amino acids, …. and ….

contact, u tube, filter, pores, large, small, prevent, bacterial, pressure, suction promotes

• bernard david later showed that the bacterial strains must make physical … for transfer of genetic material to occur

  • he used an apparatus known as …. ….

    • it contains a …. at the bottom which has ….. that were:

      • … enough to allow passage of the genetic material

      • but …. enough to …. passage of … cells

      • application of …. or … …. movement of liquid through the filter

donor, f, fertility, plasmid, extra chromosomal

• the term conjugation refers to the transfer of DNA from one bacterium to another following direct cell to cell contact

  • many, but not all, species of bacteria can conjugate

  • and only certain strains of a bacterium can act as … cells

    • in E. coli those strains contain a small circular piece of dna termed the … factor (for ….. factor)

      • strains containing the F factor are F+

      • lacking it are F-

      • the F factor is a ….

    • plasmid is the general term used to describe … …. DNA

circular, bacteria, eukaryotic, thousand, 500,000

• most plasmids are …, although some are linear

  • present in many … and a few … cells

  • range in size from a few …. to ….. bp

replication, origin, independent, single, not, survival, growth, episomes, F

• plasmids have their own …. of …

  • replicate …. of bacterial chromosome

  • can exist as a …. copy up to 100 copies

  • plasmids are usually …. required for ….

  • can provide … advantages to the bacteria

  • plasmids that can integrate into the chromosome are called ….

    • … factor can integrate

conjugative plasmids, transfer

plasmids which are transmitted via conjugation are termed … … (carry genes required for conjugation)

these genes play a role in the … of DNA

donor, recipient, sex pili, F pili, F±, attachment, F-

• the 1st step in conjugation is the contact between …. and …. cells

  • this is mediated by … … (or … …) which are made only by …. strains

    • these pili act as … sites for the … bacteria

shorten, closer, conjugation bridge, 2, stimulates, donor, transfer

• once contact is made, the pili ….

  • donor and recipient cells are drawn … together

  • a … … is formed between the … cells

• the successful contact … the … cell to begin the …. process

relaxosome, transfer, F, cut, DNA, ds plasmid, separate, accessory, relaxosome, relaxase, cut, ssDNA, nucleoprotein, exporter, 10, 15, F, inner, outer, DNA, relaxase, recipient

• …. proteins recognize the origin of … in the … plasmid, make … in the …., and separate the … ….

• as the strands …, … proteins of the …. are released

• one protein, …. , remains bound to the … end of the … (…..)

• the … is a complex of …-…. proteins encoded by the … factor that span both … and …. membranes - facilitates the transfer of the …./…. complex to the …..

dna, relaxase, F-, double, relaxase, single, double

• the exporter pumps the …/… complex into the recipient cell

• in the donor cell, the .. factor DNA is replicated to. become …. stranded

• in the recipient cell, ….. joins the ends of the … stranded DNA

  • it is also replicated to become … stranded

Hfr, high frequency, recombination, F, Hfr, plasmid, integrate, chromosome

• conjugation via Hfr strains:

  • a strain of E. coli was discovered in the 1950s that was very efficient at transferring chromosomal genes

    • called this strain …. (for …. …. of ….)

  • when an … factor integrates into the chromosome, it creates an …. cell

  • an episome is a segment of DNA that can exist as a … and can … into the …..

transfer, bacterium, bacteriophage, virus, bacterial, lytic, lysogenic

• Bacterial Transduction

  • transduction is the … of DNA from one … to another via a ….

  • a bacteriophage is a … that specifically attacks …. cells

    • depending on the type of virus, it may follow one of 2 different cycles, or both

      • ….

      • …..

injects, cytoplasm, synthesis, fragments, lyses, releases, bacterial

Lytic cycle:

• phage … its dna into …

• phage dna directs the …. of many new phages

  • host dna is digested into ….

• cell … and … new phages

• new phages can bind to .. cells

integrates, prophage, divide, dormant, excised, lytic

• Lysogenic cycle

  • phage DNA … into host chromosome

  • … DNA is copied when cells …

    • prophage can exist in a … stage for a long time

  • on rare occasions, a prophage may be … from host chromosome

  • it can switch to the … cycle

virulent, temperate

… phages only undergo a lytic cycle

… phages can follow both cycles

p22, salmonella, p1, e. coli, temperate

Transduction

• phages that can transfer bacterial DNA include:

  • …., which infects …

  • …. which infects …

  • both are … phages

lytic, his+, fragments, dna, proteins, host, chromosome, his+, transducing, recipient, his-, transduced, recombined, recipient, his+

Generalized transduction:

• this phage enters … cycle

• phage infects bacterial cell that is ….

• host dna is digested into … and phage … and … are made

• phages assemble; occassionally a phage carries a fragment of the … cell ….

  • in this case, it carries the … gene

• ….. phage injects its dna into a … cell that is …

• the … dna is .. into the chromosome of the .. cell

• the recombinant bacterium’s genotype has changed from his- to …

extracellular dna, dead, griffith, strep, natural, without, artifical, with

bacterial transformation

• transformation is the process by which a bacterium will take up … …. released by a … bacterium

• it was discovered by frederick … in 1928 while working with strains of …

• there are 2 types:

  • … transformation

    • dna uptake occurs …. outside help

  • …. transformation

    • dna uptake occurs … the help of special techniques

competent, proteins, competence factors, binding, uptake, incorporation, chromosome

Bacterial transformation:

• natural transformation occurs in a wide variety of bacteria

• bacterial cells able to take up DNA are termed … cells

  • they carry genes that encode … called … …

    • these proteins facilitate the …, …. and subsequent … of the dna into the bacterial ….

fragment, surface receptor, competent, extracellular endonuclease, smaller, degraded, single, uptake, homologous, incorporated, homologous recombination, heteroduplex, lys-, lys+

Transformation:

• dna … binds to a cell … … of a … bacterium

• an .. … cuts the dna into … fragments

• one strand is … and a …. strand is transported into the cell via an …. system

• the dna strand aligns itself with a …. region on the bacterial chromosome

• the dna strand is … into the bacterial chromosome via … …

• the … dna is repaired in a way that changes the … strand to create a … gene

random, nonhomologous, illegitimate, same, related, competence stimulating peptide, same, dna uptake signal sequences, 9, 10, 1, 2000, prefer

Transformation

• sometimes, the dna that enters the cell is not homologous to any genes on the chromosome

  • it may be incorporated at a … site on the chromosome

  • this process is termed … or …. recombination

• some bacteria prefer to take up dna from the … or a … species

  • strep secretes a … … … which leads to competence only when many cells of the … species are nearby

  • other species use .. .. .. ..

    • .. or .. bp long

    • repeated ..-… times throughout genome

    • dna with this sequence is … taken up

calcium chloride, high, shock, permeable, small, molecules, electroporation, permeable, external electrical

• Artificial transformation

  • laboratory method commonly used to get plasmids into cells

  • common method is to treat with .. .. and a … temperature ..

    • makes the cells … to …. dna …

  • … makes cells …. with … … field

horizontal, direct offspring, conjugation, transformation, transduction, within, between, antibiotic resistance

Medical relevance of bacterial genetic transfer

• …. gene transfer

  • process in which an organism receives genes from another organism without being a … ..

  • …., …., and … are examples

  • can occur … and also … species

• the types of genes acquired through horizontal gene transfer are quite varied and include genes that confer … ….

resistance, infections, breakdown, pump, out, block, inhibiting, enterococus faecalis, mrsa, skin, death

• Horizontal gene transfer has dramatically contributed to the phenomenon of acquired antibiotic ….

  • antibiotics are widely used to treat human … and increase health and size of livestock

  • bacteria can acquire genes that … the antibiotic, … it …. of the cell, or … its … effects

  • bacterial resistance to antibiotics is a serious problem worldwide

    • some strep strains are resistant to methicillin and all penicillins

    • resistance probably acquired by horizontal transfer from … …

      • these … strains cause serious … infections and sometimes ….