Lecture 6 Guide

Lecture 6 Guide - 
 
 
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Unformatted text preview: 
 
 
 
Genes
and
Interactions
 I.  II.  Complementation
Test
 
 A.
Defining
the
number
of
genes
 Biochemical
Pathways
 
 A.
One
Gene
One
Enzyme
 III.  Analysis
of
Double
Mutants
 
 A.
Epistasis
 
 B.
Suppressors
 
 
 
 
 

 1 
 
 
 

 

 Objectives: 
 
 
 Know
how
to
do
a
complementation
test
and
determine
the
number
of
genes
 Be
able
to
determine
a
biochemical
pathway
from
mutant
phenotypes
 Understand
the
effects
between
genes
for
epistasis
and
suppression 

 2 Complementation Complementation testing tells us whether two mutations are in the same or different genes. Starting point: Different pure breeding lines that are recessive and effect the same trait 7-3 Complementation
testing
tells
us
whether
two
mutations
are
in
the
same
or
different
genes.
 4
 Example
I:
Two
recessive
pure
breeding
strains
that
both
have
black
body
mutant
color.
 Question:
Are
these
mutations
in
the
same
gene,
or
in
two
different
genes?
 Procedure:
Cross
mutant
strains
to
each
other.
 Result:
F1
progeny
all

have
wild
type
 body
color,
i.e
the
mutations

 complemented
each
other.
 Conclusion:
Body
color
is
controlled

 by,
at
least,
two
genes.
 5
 Example
2:
Nine
strains
that
effect
eye
color.
 b. Crosses of the 9 strains show mutant (-) or wild type (+) eye color in the F1 progeny. Table of this data shows five complementation groups, i.e. 5 different genes, for eye color. c. Recombination mapping demonstrates distance between genes and alleles. 7‐6
 Isolation of an arginine auxotrophic mutation Figure
6‐11
 7
 Inferred
pathway:
 Gene












arg‐1






























arg‐2




























arg‐3
 
 



enzyme
x





















enzyme
y




















enzyme
z
 Precursor


‐‐‐‐‐‐‐‐‐‐



ornithine


‐‐‐‐‐‐‐



citrulline


‐‐‐‐‐‐‐‐‐




arginine
 8
 Interaction between a regulatory protein and its target Figure
6‐18
 9
 Recessive
epistasis:


9:3:4
ratio,

e.g.
labrador
yellow
coat
mutation
 Dominant
epistasis:


12:3:1
ratio
e.g.
foxglove
white
mutation
 10
 A molecular mechanism for suppression Figure
6‐22
 11
 A model for synthetic lethality Figure
6‐23
 12
 Assignment

 Achieve
Objectives
List
(slide
2)
through
study
 and
practice.
 Solve
problems
from
textbook.

 Chapter
6:
 4,
49
ab,
55,
66
 13 ...
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This note was uploaded on 09/26/2009 for the course BIS 98659 taught by Professor Kimbrell during the Summer '09 term at UC Davis.

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