Chapter 7: Genetic Transfer & Mapping in bacteria Flashcards
Why do bacteria rely on genetic transfer?
- since they are haploid
- reproduce asexually via binary fission
- so a segment of bacterial DNA is transferred from one bacterium to another
Gram positive bacteria
has a thick peptidoglycan layer
- stains purple
ex: streptococcus (strep throat), staph infection
Gram negative bacteria
thin layer of peptidoglycan layer in the middle. has an outer lipid bilayer and bottom cell membrane layer
- stains pink
ex: E.Coli
Prototrophs
- Wild type
- grow on minimal media
Auxotrophs
- unable to synthesize essential nutrients
- grow on complete media or minimal media + additional nutritional supplement
What is minimal media?
inorganic salts, water, carbon source (sugar)
E.coli strain with genotype trp- ade- thi+ will?
- not grow on minimal media
- cannot produce trp
-cannot produce ade - can produce thi
What do we need to add to minimal media to get this E.coli strain to grow?
trp+
ade+
List characteristics of Plasmids (9)
- general term to describe extra-chromosomal DNA
- most are circular but some are linear
- present in many bacteria and a few eukaryotic species
- range in size (small to 500,000 basepairs)
- own their own replication of origin
- replicate independent of bacterial (host) organism
- can exist as single copy or up to 100 copies per cell
- not required for survival
- can provide growth advantages to bacteria
What are the 3 genetic transfers in bacteria?
- conjugation - direct physical contact
- involves bacteriophages
- involves uptake from the environment
What type of transfer is it?
- From donor to recipient (unidirectional)
- horizontal gene transfer
- no complete diploid stage is formed
What is transformation?
the process by which a bacterium will take up extracellular DNA released by a dead bacterium
What are the 2 types of transformation?
- transformation with DNA fragments (coil pieces that get integrated into the bacterial chromosome) could be unsuccessful
- transformation with plasmids (stable) (plasmid just inserts itself into the bacteria)
List the 3 ways bacteria are artificially competent
- heat shock (raise it to 38-39C)
- electro shock
- chemical treatment
What are the two direct physical contact for conjugation?
- sex pilus
- mating bridge
How did Bernard Davis figure out the conjugation requires physical contact?
through a U-tube
What is the F factor?
- F factor or fertility factor
- F+ = strains containing F factor
- F- lacking f factor
- small circular piece of DNA
Draw out process of F Factor
- Relaxosome recognizes origin of transfer (DNA sequence); makes a cut in DNA
- After cutting, most accessory proteins of the relaxosome are released
- one protein, relaxase, remains bound to the end of the T-DNA
- Exporter is a complex of 10-15 proteins encoded by the F Factor that span both inner and outer membranes; pumps DNA/relaxase into recipient cell
What happens when an F Factor integrates into a chromsome?
it creates an HFR cell and becomes Fâ (f prime)
What is agrobacterium?
DNA that can be conjugated from bacterial donors to eukaryotic recipients
- causes crown galls (tumor like) on trees
List the characteristics of Transduction
- transfer of DNA from one bacterium to another via a bacteriophage
What is a bacteriophage?
- a virus that specifically infects bacterial cells
- composed of genetic material surrounded by a protein coat
- could be lytic or lysogenic
Lytic means
it kills bacteria
Lysogenic means
integrates into bacteria
