Upload
kunjal
View
219
Download
0
Embed Size (px)
Citation preview
8/8/2019 Microbial Genetics Gene Transfer SP10
1/22
Microbial Genetics
Gene Transfer
Chapter 8
8/8/2019 Microbial Genetics Gene Transfer SP10
2/22
Genetic Recombination
Vertical genetransfer: Occursduring reproduction
between generationsof cells.
Horizontal gene
trans
fe
r: The transferof genes between cellsof the same
generation.
8/8/2019 Microbial Genetics Gene Transfer SP10
3/22
Horizontal Gene Transfer
1. Transformation
2. Transduction
3. Conjugation
8/8/2019 Microbial Genetics Gene Transfer SP10
4/22
1. T R A N S F O R M A T I O N
Genes are transfer red from one
in solution.
a. naturally occurs in a few bacter iaCompetent
b. bacter ia madecompetent ar tificiallyc. approx 20 genes
8/8/2019 Microbial Genetics Gene Transfer SP10
5/22
Figure 8.24
Genetic Transformation
8/8/2019 Microbial Genetics Gene Transfer SP10
6/22
Transformation
8/8/2019 Microbial Genetics Gene Transfer SP10
7/22
2. Transduction
Transport of DN A from one bacter ium toanother bacterium by a virus
a. Generalized vsspecialized transduction
b. dur ing assembly: defective phage
c. Defective phagecan now transfer DN Afrom host (the Donor) to anotherbacter ium (Recipient)
8/8/2019 Microbial Genetics Gene Transfer SP10
8/22
Figure 8.28
Generalized Transduction by a Bacteriophage
8/8/2019 Microbial Genetics Gene Transfer SP10
9/22
2
3
4
5
6
Figure 13.13
Specialized Transduction
8/8/2019 Microbial Genetics Gene Transfer SP10
10/22
Trans
duc
tion
8/8/2019 Microbial Genetics Gene Transfer SP10
11/22
3. C O N J U G A T I O N
D i rect transfer of DN A from bacterialdonor cell to a recipient.
a. Mediated by plasmidb. requirescell to cell contact: established
by pil i in most G ram negativecells
c.
Spread of Antibiotic resistanced. Plasmid or Chromosome moves as
8/8/2019 Microbial Genetics Gene Transfer SP10
12/22
Conjugation:Transfer of a plasmid
1. Donor cell has F plasmid and hence isrefer red to as
2. Recipient cell lacks F plasmid, henceF
3. Only onestrand of plasmid
trans
fe
r re
d4. After conjugation, both donor andrecipient become F+
8/8/2019 Microbial Genetics Gene Transfer SP10
13/22
Figure 8.27a
Conjugation in E.coli
8/8/2019 Microbial Genetics Gene Transfer SP10
14/22
Conjugation
http://../animations_library/anim0020.exehttp://../animations_library/anim0020.exe8/8/2019 Microbial Genetics Gene Transfer SP10
15/22
Plasmids
1.
One/Many types of plasmids in a singlecelleg. F , R ,T i.
2. A few or several copies of a plasmid(high/low copy number plasmid)
3. Narrow/broad range plasmids
4. Nonessential functionscarr ied onplasmids-spontaneous deletion
5.
replicate
8/8/2019 Microbial Genetics Gene Transfer SP10
16/22
Conjugation:Transfer of a plasmid
and chromosomal DN A1. Donor cell is Hfr : has F plasmid. How
is it different from F+?
2. Recipient cell lacks F plasmid, hence F
3. Hfr cell conjugates with F cell
4. End result: H fr cell and recombinantF cell
8/8/2019 Microbial Genetics Gene Transfer SP10
17/22
Figure 8.27b
Conjugation in E.coli
8/8/2019 Microbial Genetics Gene Transfer SP10
18/22
Figure 8.27c
Conjugation in E.coli
8/8/2019 Microbial Genetics Gene Transfer SP10
19/22
Conjugation: Chromosomal transfer
8/8/2019 Microbial Genetics Gene Transfer SP10
20/22
Figure 8.30a, b
Transposons Segments of DN A that can move from one
region of DN A to another Contain insertion sequences for cutting and
resealing DN A (transposase)
Complex transposonscar ry other genes
8/8/2019 Microbial Genetics Gene Transfer SP10
21/22
TRANSPOSONS
all transposonscontain info needed toinsert selves in genetic material
frequency similar to spontaneousmutations
involvement in evolution of organisms
--can car ry genes with them;
e.g. antibiotic resistance
8/8/2019 Microbial Genetics Gene Transfer SP10
22/22
Transposons