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Lecture 6

BIOC 4403 Lecture Notes - Lecture 6: Gene Expression, Govia, Enterocyte


Department
Biochem & Molecular Biology
Course Code
BIOC 4403
Professor
Archibald John
Lecture
6

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1. Lateral gene
transfer or
horizontal gene
transfer (LGT /
HGT)
The movement of genetic material
between different species in a manner
other than 'traditional' reproduction.
Contrasted with vertical transfer, the
transmission of genes from the parental
generation to offspring via sexual or
asexual reproduction.
2. Traditional
reproduction
vertical transfer of genes from parent to
offspring via sexual or clonal
reproduction
3. How do we detect
'foreign' genes in a
genome? And how
do we determine
where they come
from?
-gene presence / absence
-compositional anomalies / genomic
landscape
-phylogenetic incongruence
4. Prokaryotes
mechanisms of
gene transfer
Bacterial transformation: naked DNA;
Bacterial transduction: by virus;
Bacterial conjugation: physical contact.
5. Bacterial
transformation
6. Bacterial
transformation:
general
mechanism
Genetic material in the form of "naked"
deoxyribonucleic acid (DNA) is
transferred between microbial cells.
The genetic alteration of a cell resulting
from the direct uptake and
incorporation of exogenous genetic
material (exogenous DNA) from its
surroundings and taken up through the
cell membrane(s)
7. Bacterial
transduction
8. Bacterial
transduction:
general
mechanism
a process of genetic recombination in bacteria
in which genes from a host cell (a bacterium)
are incorporated into the genome of a
bacterial virus (bacteriophage) and then
carried to another host cell when the
bacteriophage initiates another cycle of
infection.
9. Bacterial
conjugation
10. Bacterial
conjugation:
general
mechanism
sexual process in which two lower organisms
of the same species, such as bacteria,
protozoans, and some algae and fungi,
exchange nuclear material during a
temporary union, completely transfer one
organism's contents to the other organism
(bacteria and some algae), or fuse together to
form one organism (most bacteria and fungi
and some algae)
11. ICEs Integrative and conjugative elements.
A type of mobile elements.
12. Integrative
and
conjugative
elements
Bacterial mobile genetic elements that
primarily reside in the host chromosome, but
can excise and be transferred to other cells
by conjugation.
13. Integrative
and
conjugative
elements:
properties
-ICEs are highly mosaic: they contain a variety
of different genes associated with conjugation
and mobility.
-Integration / excision mediated by integrase
and excisionase proteins, which mediate DNA
recombination at 'att' sites in the bacterial
chromosome and ICE sequences.
14. Example of
ICEs
SXT family of ICEs, found in Vibrio cholerae
and related bacteria. 52 genes in total. Confer
multi-drug resistance and other adaptive
features to their bacterial hosts.
15. Common
places for
Integration &
Conjugative
transfer
-Integration of ICEs often occurs at tRNA
genes.
-Conjugative transfer typically occurs via
assembly of a 'type IV secretion system',
through which DNA passes by rolling circle
replication.
.
.
.
.
4403 - 6. Prokaryotic genomes II
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