iii. linkage a. ‘complete’ linkage b. ‘incomplete’ linkage
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III. Linkage
A. ‘Complete’ Linkage B. ‘Incomplete’ Linkage C. Three-point Mapping
- combine complementary sets
Three Point Test Cross
AaBbCc x aabbcc
Phenotypic Ratio:
ABC = 25ABc = 3Abc = 42AbC = 85aBC = 79aBc = 39abc = 27abC = 5
ABC = 25abc = 27 52ABc = 3abC = 5 = 8
Abc = 42aBC = 39 81
AbC = 85aBc = 79 164
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Bacterial Genetics
Copyright © 2010 Pearson Education, Inc.
Bacterial Genetics
I.Overview - Domains of Life
Copyright © 2010 Pearson Education, Inc.
Bacterial Genetics
I.Overview - Domains of Life
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission
= 10 billion cells
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fissionThe rapid production of new
organisms creates genetic diversity by mutation, alone; even though the rates of mutation are low for any given gene.
Consider an average gene mutation rate = 1 x 10-5 (meaning a new mutation is produced in every 100,000 copies… or descendants).
In 10 billion (1010) descendants, there would be 105 different mutations at this one gene.
This is happening independently across 4000 (4 x 103) genes in the E. coli genome.
So, in that population of 10 billion cells, there might be as many as 4 x 108 different genomes. About 1/3 will be “silent” (not change the AA), and many will result in a lethal mutation so they won’t occur. But still….. VARIATION.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation
Copyright © 2010 Pearson Education, Inc.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation
Lederberg and Tatum – 1946
- certain strains of bacteria are able to donate genes to other strains – they have a “fertility factor” (F+). Other strains lack this factor (F-).
Copyright © 2010 Pearson Education, Inc.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation
Davis demonstrated that cell-cell contact was required…
Copyright © 2010 Pearson Education, Inc.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation
F -duction
Copyright © 2010 Pearson Education, Inc.
Figure 8-6And Cavalli Sforza isolated a strain that would cause genetic change at a very high rate: Hfr (High frequency recombination). He recognized that the acquisition of traits was related to the duration of the conjugation event.
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He hypothesized that the time between transfer to the recipient cell was related to the distance between genes.
As such, if he interrupted mating at specific intervals, he could use time between trait acquisition as an index of distance between genes.
Copyright © 2010 Pearson Education, Inc.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation
He isolated different strains that transferred genes in different order, suggesting that the transfer process could begin at different places.
Copyright © 2010 Pearson Education, Inc.
Figure 8-8bHe isolated different strains that transferred genes in different order, suggesting that the transfer process could begin at different places.
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Figure 8-9 part 1
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Figure 8-9 part 2
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Figure 8-9 part 3
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Figure 8-9 part 4
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Figure 8-9 part 5
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An integrated Hfr plasmid can revert to a free F+ plasmid, and take chromosomal genes along, too.
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An integrated Hfr plasmid can revert to a free F+ plasmid, and take chromosomal genes along, too.
It is now an F’ plasmid.
Conjugation can now occur.
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Figure 8-10 part 4
Copyright © 2010 Pearson Education, Inc.
Figure 8-10 part 5
video
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation 2. transformation – absorption of DNA from the environment.
Copyright © 2010 Pearson Education, Inc.
Figure 8-12 part 1
Copyright © 2010 Pearson Education, Inc.
Figure 8-12 part 2
Copyright © 2010 Pearson Education, Inc.
Figure 8-12 part 3
Copyright © 2010 Pearson Education, Inc.
Figure 8-12 part 4
Copyright © 2010 Pearson Education, Inc.
Figure 8-12 part 5
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic Reproduction
A. fission B. “sex” – genetic recombination
1. conjugation 2. transformation – absorption of DNA from the environment. 3. viral transduction
Copyright © 2010 Pearson Education, Inc.
Figure 8-14
Copyright © 2010 Pearson Education, Inc.
Figure 8-17
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic ReproductionIII.The Use of Bacteria in Recombinant DNA Technology
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic ReproductionIII.The Use of Bacteria in Recombinant DNA Technology
Plasmid ‘vector’ with ampicillin-resistance gene
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic ReproductionIII.The Use of Bacteria in Recombinant DNA Technology
Transformation: absorption of plasmids
Plasmid ‘vector’ with ampicillin-resistance gene
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic ReproductionIII.The Use of Bacteria in Recombinant DNA Technology
Transformation: absorption of plasmids
Plasmid ‘vector’ with ampicillin-resistance gene
Grow on selective media with ampicillin; only bacteria that have absorbed plasmids will grow.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic ReproductionIII.The Use of Bacteria in Recombinant DNA Technology
Transformation: absorption of plasmids
Plasmid ‘vector’ with ampicillin-resistance gene
Grow on selective media with ampicillin; only bacteria that have absorbed plasmids will grow.
Fission produces millions of cells in a day that have each plasmid – colonies.
Bacterial Genetics
I.Overview - Domains of LifeII. Prokaryotic ReproductionIII.The Use of Bacteria in Recombinant DNA Technology
Show the location of all ampicillin-resistant colonies
Transfer to a piece of filter paper with a radiolabeled probe specific to the gene in question
Take an x-ray to identify colonies that have absorbed the plasmid with the gene of interest. Culture the bacteria, cloning the gene for study.
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