class #4- bacterial genetics Flashcards
what is a bacteriophage
a virus that parasitizes a bacterium by infecting it and reproducing inside it
what is the lytic cycle
-injection of phage dna
-replication & synthesis of new phage particles
-packaging of DNA into heads
-lysis
-infection (start again)
what is lysis
disintegration of cell by rupture of cell wall or membrane (killing)
what is the hershey heaven and the waring blender experiment
an experiment to prove dna is genetic material using s35 (radioactive sulfur) and p32 (radioactive phosphorus)
what was the role of s35 in hershey ex
to label protein
what was the role of p32 in hershey ex
to label the dna
what happened in the hershey ex
- let phage absorb to bacteria then put in blender
- separate phage from bacteria: s35 went with phage(virus) and p32 when with bacteria
how did the hershey experiment prove that dna was genetic material
p32 was detected in cells (was in dna) s35 was not detected in cells (was in protein)
what is a phage plaque
zone of lysed bacteria
what is a turbid plaque
created by a lysogenic phage
what is turbidity caused by
Caused by bacteria that have been infected and the phage has integrated into the genome
what is generalized transduction
The process by which phages can package any bacterial DNA (chromosomal or plasmid) and transfer it to another bacterium.
where does generalized transduction occur
during the lytic cycle
what happens during generalized transduction
host dna is degraded and bits are mistakenly packaged along with phage dna, host dna is now transferred to another host
is generalized transduction efficient
no, b/c only a single phage is getting packaged with dna from host
what is transformation
the uptake of naked dna.
what important experiment used transformation to show that DNA is genetic material?
Griffiths experiment (rats, s strain and r strains)
what are the most desperate ways to transform DNA
-biolistic transformation
-electroporation
what is naturally competent bacteria
bacteria that are naturally “competent” to take up DNA, they have structures & systems dedicated to taking up dna
who is Joshua Lederberg
he coined the term “plasmids”, nobel prize for conjugation 1959
what is conjugation
bacterial “sex”, where one bacterium transfers genetic material to another through direct contact
what are self-transmissable plasmids
they encode machinery to iniate conjugation and transfer plasmid
what is a mobilizable plasmid
can be transferred but need Tra functions supplied in trans
role of donor and recipient in conjugation
donor- has plasmid
recipient - gets plasmid
how is dna transferred in conjugation
rolling circle replication, direct contact between 2 bacteriums
what is CRISPR
adaptive immunity for bacteria
Clustered Regularly Interspaced Short Palindromic Repeats
what are CAS
CRISPR associated genes
how does CRISPR work
- the array is transcribed
- Cas gene products process array
- crRNA has a piece that is bound by the Cas9
- crRNA-Cas9 complex can recognize specific DNA sequences
what are transposons
DNA elements that ecode transposase,
they insert randomly
role of transposase
they copy a short sequence of DNA and allows DNA to ‘jump’
what is Barbara McClintock’s main contribution
she developed notion of gene regulation
what is target duplication
it follows after insertion, duplicates a small genetic sequence
what aids in duplicating a target sequence
transposase
what is a promoter
A region of DNA upstream of a gene where relevant proteins bind to initiate transcription of that gene.
what does a promoter drive
drives the expression of a single gene, or mulitple genes (co-expression)
what is an operon
where genes that are co-expressed are found
what is an activator
proteins that bind to DNA at sequence sites to promote RNA polymerase function
who is Jacques Manod and what did he contribute
-founder of molecular bio
-worked out lac operon and trp operon
what is a repressor
they block binding of RNA polymerase to promoter
their ability to bind DNA is often regulated by cofactors (sugars or other metabolites)
in the lac operon, what is the uninduced state
lacl (repressor) binds to operator
no transcription
what is a non-inducible mutant
lacZ, the Lacl repressor can no longer bind to lactose
in the lac operon, what is the induced stat:
-the inducer (lactose) binds Lacl (repressor)
-and Lacl cannot bind to operator
-transcription of operon
what is a constitutive mutant
when lacl: no repressor, no repression
and Oc: repressor binding site damaged, Lacl is made but cannot bind
what is a cis mutation
cis-acting locus: a genetic region affecting the activity of genes on that same DNA molecule
what is a trans mutation
trans-acting locus: encodes for a factor that can act else where
