Genetics Ch. 7
lederberg, tatum
1946 - discovered genetic transfer in bacteria (2)
conjugation, transduction, transformation
3 types of horizontal gene transfer
Pilus
A tube that allows bacteria to transfer genetic material during conjugation.
proteins, F-factor, membrane
At the start of conjugation, the exporter a complex of 10-15 _____________ encoded by the __________ that span both inner and outer ____________, pumps the DNA Relaxase complex into the recipient cell
artificial transformation
DNA uptake occurs w/ the help of lab equipment
natural transformation
DNA uptake occurs w/out outside help
u-tube
Davis used a ____________ apparatus -- filter w/ pores large enough to allow genetic material, but block bacterial cells
plasmid
F+ ______ has its own origin of replication, exists as a single copy separate from chromosome
within, between
HGT can occur _____ and ______ species
acquired antibiotic resistance
HGT has dramatically contributed to the phenomenon of...
high frequency of recombination
Hfr stands for
F+
Hfr strains derives from ___ strains
F factor
In E. coli, strains contain a small circular piece of DNA termed ____________ plasmid (+: with; -: without)
mutations
____ in phages genome alters ability to produce plaques
natural
______ transformation occurs in a wide variety of bacteria
bacteria, viruses
__________ and __________ account for 1/4-1/3 of human deaths worldwide
davis
__________ later showed bacterial strains must make physical contact for transfer to occur
bacterial resistance
____________ to antibiotics is a serious worldwide problem
distance between genes
_______________ is determined by comparing their times of entry during an uninterrupted conjugation experiment
Relaxase
accessory protein released from relaxosome that remains bound to the end of the t-DNA
haploid
bacteria are usually _____________
asexually
bacteria reproduce _____________
competent cells
bacterial cells able to take up DNA
genetic material, protein coat
bacteriophages are composed of ___________ surrounded by a _____________
bacteria
can acquire genes that breakdown the antibiotic, pump out of cell/block inhibiting effects
auxotrophs
cannot synthesize a needed nutrient
calcium chloride, high temp shock
cells can be made competent in the lab by treatment w/ ________ and _____________
plaque
clear area on otherwise opaque bacterial lawn on agar surface of petri dish
Benzer
collected many rll mutant strains that can form large plaques in E. coli B and none in E. coli k12
competence factors
competent cells carry genes that encode proteins called...
HGT
conjugation, transformation and transduction are examples of...
order, distance
cotransduction is used to determine the ______ and ______ between genes that lie fairly closely together
Hayes
demonstrated conjugation between an Hfr and F- strain involves transfer of a portion of the Hfr bacterial chromosome
Cavalli-Sforza
discovered a strain of E. coli that was efficient at transferring chromosomal genes -- Hfr (1950s)
Griffith
discovered transformation in 1928 while working w/ strains of Streptococcus pneumoniae
conjugation bridge
during conjugation, a _____________ provides a passageway
competence factors
facilitate binding, uptake, and subsequent incorporation of DNA into bacterial chromosome
plasmid
general term used to describe extra chromosomal DNA, that is usually not required for survival of cell, can provide advantages in certain environments
1.5-2 hours
generally, it takes _________ for the entire Hfr chromosome to be passed into the F-cell
genetic diversity
genetic transfer in bacteria enhances...
+
genotype of bacterial cells that grew on plates has to be: met__, bio__, the__, leu__, thi__
dna repair enzymes
heteroduplex DNA is repaired by...
imprecise
in some cases, the integrated F factor is excised in an __________ fashion
heteroduplex
in transformation, a region of mismatch caused by sequence differences between the two alleles
bacteriophage
virus that specifically attacks bacterial cells
are not
viruses _____ living
traits
viruses have unique biological structures/functions, and therefore have...
existence, replication
viruses rely on host cell for _____ and _________
bacteriophage
viruses that infect bacteria, contain their own genetic material that governs traits
antibiotics
widely used to treat human infections and increase health/size of livestock
conjugation
type of horizontal gene transfer that involves direct physical contact
transformation
type of horizontal gene transfer that involves uptake from the environment
transduction
type of horizontal gene transfer that involves viruses
antibiotic resistance, virulence
types of genes acquired through HGT are varied and include genes that confer _____________ and _________
natural, artificial
types of transformation (2)
minutes
units of conjugation, refer to relative time it takes for genes to first enter an F- recipient during experiment
e. coli
lederberg and tatum were studying strains of _______ that has different nutritional growth requirements
prototrophs
make all their nutrients from basic components
conjugate
many, but not all bacteria can ____________
complementation test
method of discovering whether two mutations are in the same or separate genes
do not
most conjugations ________ last long (only a portion of Hfr chromosome gets into the F- cell)
dominant, loss of functions
mutations are not masked by ___________ genes, which makes it easier to identify _____________ mutations in bacteria than in eukaryotes
donor
only certain strains of bacterium can act as _____ cells
lysis, phages
plaque is caused by the ____ of bacterial cells as a result of the growth/replication of ______
are, easy
plaques _______ visible to the naked eye, so mutation is ____ to genetically analyze
transformation
process by which a bacterium will take up extracellular DNA released by damage or dead bacteria
horizontal gene transfer
process in which an organism receives genes from another organism w/out being a direct offspring
Relaxosomes
protein complex encoded by the F-factor. makes a cut at the origin of transfer and begins to separate the DNA strands
DNA Relaxase complex
recognized by the coupling factor and transferred to the exporter
cotransduction
refers to the packaging and transfer of two closely-linked genes
conjugation
refers to the transfer of DNA from one bacterium to another following direct cell-to-cell contact
genetic transfer
researchers rely on ____________, a segment of bacterial DNA transferred from one bacterium to another
electroporation (electrical shock)
secondary way cells can be made permeable to DNA
episome
segment of DNA that can exist as a plasmid and can integrate into the chromosome
chromosome DNA, recombine
the F- cell picks up __________ from the Hfr cell, can _______ w/ the homologous region on chromosome of recipient cell
bacterial chromosome
the integrated F factor may carry genes that were once found on the __________ (F' factors)
transduction
transfer of DNA from one bacterium to another via a bacteriophage