chapter 6 Flashcards
3 advantages of using bacteria for genetics studies
- repro fast + many progeny
- haploid genome (all mutations expressed immediately)
- spontantous mutations
haploid genome meaning
one copy of gene per cell, all mutations expressed immediately
prokaryotes have ____ chromosome transfer
partial
how is the haploid state restored
recombination
exchange of genetic material reveals _____
linkage
prototrophs
wild type bacteria that can grow on minimal media
auxotrophs
mutants that can’t grow unless media is supplemented with specific compounds
metabolic mutants
cannot utilize specific compounds (ex: lactose, galactose)
resistance mutants
can grow in presence of inhibitors (ex: antibiotics)
bacterial genome characteristics
haploid chromosomal DNA, repro by cell division (identical daughters)
plasmids
extra DNA elements, small circular DNA molecules
F factor
fertility factor, carries gene mating promoters between bacteria
R factor
resistance factor, carries genes with antibiotic resistance
col-plasmids
code for colicens (toxins for other bacteria)
virulence plasmids
enable bacteria to become pathogens (anthrax)
genes that ensure inheritance are…
F factor genes, genes w benefits (r factors, col plasmids, etc)
genes regulate _____ transfer to other cells
plasmid
sequences regulate ….
insertion into bacterial chromosome
3 methods that bacteria exchange genetic info
transformation, conjugation, transduction
conjugation
cells touch, one directional contact that mediates transfer of chromosomal or plasmid DNA
transformation
bacterial cells pick up DNA from external environment
transduction
bacteriophage transfer DNA into bacterial cell
F-factor in conjugation
F+ donor has circular F plasmid that contains origin of replication, genes for pili formation, and genes for DNA transfer
plasmid replicates itself and…
inserts single strand copy into recipient
when F+ donor transfers to F- recipient…
recipient is converted to F+ strain
HFR cell
high frequency recombination, has the F+ plasmid in the bacterial chromosome
exegenote
formed when integrated F drives linked chromosomal DNA into recipient
endogenote
transferred DNA recombines with recipient chromosome (endogenote) and restores haploid state
transfer begins at _________ and is directional
F insertion site
longer conjugation transfers ___ to donor chromosome
more
F factor enters _____ so F- rarely becomes ___
LAST, HFR
the direction of transfer is the basis of…
recombination mapping
The gene closest to the F integration site is transffered ____ and has _____ liklihood of recombination
first, higher
distant genes have ______ likilihood of recombo
lower
time transfer is ____ to distance
proportional
plasmid transfer vs chromosome transfer
plasmid: the plasmid replicates and hops into the next one
chromosome: strand is replicated and integrates into other one’s chromosome “tainted my bloodline”
recombo results from…
double chromosome cross over
double reombinants
can occur, use the product rule to calculate
F’ plasmid
when F sequences are removes from HFR impercisely so the chromosome loses genetic info
transformation source
from same/diff species, lysed dead bacteria, or secretions from other bacteria
competent
bacteria capable of transformation
incoming DNA must ____ host
match
bacteriophage
inject their DNA into bacterial cell and hijack cell machinary to replicate it’s own DNA
Two types of transduction
generalized and specialized
generalized transduction
any gene may be transferred, phage picks up pieces of bacterial chromosome by mistake and put them in another cell
specialized transduction
only a few genes are transferred
co transduced genes are…
closely linked
the greater the frequency of co-transduction, the ________ the two genes are to each other
closer
high frequency cotransfer indicates…
tighter linkage
if no recombo, expect
only parental genotypes in progeny
if recombo, expect
recombinants (like h+ r+ and h r)
phage can recombine in mixed infections
an produced recombo
parental + recombo / total
generalized transduction using phage can transfer ____ region of bacterial chromosome into recipient
any
specialized transduction transfers ____ regions into recipient cells
specific
