Download Complementation

6/27/17
BIOLOGY 207 - Dr.Locke
Lecture#4 – Complementation
Required readings and problems:
Reading: Open Genetics, Chapter 3 , 4.5
Problems: Chapter 3. 4.5
Optional
Griffiths (2008) 9th Ed. Readings: pp 235-239
Problems: 9th Ed. Ch. 6: 1-7, 25, 28, 50
Campbell (2008) 8th Ed. Readings: ?
Concepts:
How can we determine if mutations are in the same, or different,
gene loci?
1. Mutation in different genes can be identified by
complementation tests.
2. Mutations that complement are mutant in different gene loci and are called nonallelic mutations.
3. Mutations that fail to complement (non-complementing) are mutant in the same
gene locus and are called allelic mutations.
Biol207 Dr. Locke section
Lecture#4
Fall'11
page 1
6/27/17
Complementation tests in Diploids
Complementation studies in diploids can be used to demonstrate two mutations are in
either:
 the same gene, or
 two different genes
Relation to previous section:
If two mutations are in different genes then each different gene is associated with a
different enzyme in a biochemical pathway
Previously used Neurospora
- haploid organism
- only has one copy of each gene
- used mapping of mutations to different chromosomes to establish different
genes
We can’t use complementation test in a haploid organism
-need to make it diploid -> see the phenotype of both mutations in the same diploid
cell/organism
Yeast - can be either haploid or diploid organism
Biol207 Dr. Locke section
Lecture#4
Fall'11
page 2
6/27/17
Yeast - Haploid
- simple organism -> like Neurospora
Assume the following pathway:
Substrate
Product/
Product
Substrate
1 -------------------------> 2 ---------------------------> 3
Enzyme
A
B
Gene
a+
b+
Then in haploid Yeast: a strain can be mutant or wild type at each gene
e.g.:
a+ b+ => wildtype enzymes
=>
1--------> 2----------> 3
=> growth
a+ b- => mutant enzyme B
=>
1--------> 2----------> 3
=> no growth
a- b+ => mutant enzyme A
=>
1--------> 2----------> 3
=> no growth
a- b- => mutant enzymes A &B =>
1--------> 2----------> 3
=> no growth
Biol207 Dr. Locke section
Lecture#4
Fall'11
page 3
6/27/17
Yeast can also exist as a diploid -> complementation testing
- two haploid cells come together - fuse one haploid strain with another haploid strain
e.g.:
First Strain / Second Strain
make a
Diploid strain
a+ b+
a+ b+
a+ b+ / a+ b+
Having two copies in each cell may permit complementation to take place.
Substrate
Product/
Product
Substrate
1 -------------------------> 2 ---------------------------> 3
Enzyme
A
B
Gene
a+
b+
Therefore:
1st strain &
2nd strain
a+ b- and
a+ ba- b+ and
a- b+
a- b+ and
a+ b-
Combined Outcome Conclusion:
genotype (phenotype)
a+ b- / a+ b- No growth No complementation
a- b+ / a- b+ No growth No complementation
a- b+ / a+ b- Growth
Biol207 Dr. Locke section
Lecture#4
Complementation
Fall'11
page 4
6/27/17
Complementation:
If the mutations fail to complement
then they are mutant in the same gene;
they are allelic mutations.
If the mutations do complement
then they are mutant in different genes;
they are non-allelic mutations.
Biol207 Dr. Locke section
Lecture#4
Fall'11
page 5
6/27/17
Example:
Flower – wild type is blue mutant is white
Three different mutants $ dollar
£ pound
white $ x white £
¥ Yen
white £ x white ¥
white
blue
$
£
¥
$
£
¥
wild type
NOTE: Mutations must be recessive to wild type to be used in a complementation test!
Dominant, or semi-dominant mutations CANNOT be used.
Biol207 Dr. Locke section
Lecture#4
Fall'11
page 6
6/27/17
Complementation Groups:
Complementation group =
(1) a group of allelic mutations
(2) a group of mutations that are all mutant are in the SAME gene.
(3) a group of mutations that FAIL to complement one another
(4) gene (a set of allelic mutations defines one gene) .
A “group” can consist of:
- only one mutation (it complements all the others), or
- more than one mutation (all of which are allelic mutations and don’t complement
each other).
Example:
See page on Complementation Help
http://www.biology.ualberta.ca/courses.hp/bio207.hp/locke/complementation.htm
Biol207 Dr. Locke section
Lecture#4
Fall'11
page 7