Jakob_PS7

Jakob_PS7 - Problem
Set
7
 


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Unformatted text preview: Problem
Set
7
 
 1.
Bicoid
is
one
of
several
maternal
effect
genes
required
for
the
successful
development
of
 Drosophila
embryos.

You
have
isolated
a
recessive
mutation
in
the
bicoid
gene
(bc‐).
For
 each
cross
below,
list
the
genotypes
of
all
F1
progeny
that
you
predict
will
survive
to
 adulthood.
 
 bc‐/+
female
X
bc‐/+
male
 
 
 bc‐/+
female
X
bc‐/bc‐
male
 
 
 bc‐/bc‐
female
X
bc‐/+
male
 
 
 2.
You
are
studying
a
recessive
loss
of
function
mutation
in
a
fly
gene
called
extensin.The
 mRNA
for
extensin
is
deposited
in
the
egg
by
the
mother
and
is
required
for
normal
 proportioning
of
the
adult
fly.
The
endogenous
gene
for
extensin
is
turned
on
later
in
 development
and
is
required
for
flies
to
grow
to
their
normal
size.
Predict
the
genotype
and
 the
phenotype
of
the
progeny
from
the
crosses
listed
below.
Choose
from
the
following
 phenotypes:
(1)
disproportionate;
(2)
small;
(3)
small
&
disproportionate;
(4)
wild‐type.
 
 Ex‐/+
female
X
Ex‐/+
male
 
 
 Ex‐/Ex‐
female
X
Ex‐/+
male
 
 
 +/+
female
X
Ex‐/Ex‐
male
 
 
 3.
One
of
the
characteristics
of
mitochondrial
diseases
is
that
their
phenotype
can
change
 significantly
over
time.
What
unique
feature
of
organelle
genetics
likely
explains
this
 phenomenon?
 
 
 
 4.
What
determines
sex
in
humans?
What
about
in
flies?
 
 
 
 5.
Why
do
XXX
mammals
survive
but
XXX
flies
die?
 MCB
104
–
Section
105/106
 6.
For
each
mutation
listed,
give
an
example
of
a
possible
extragenic
suppressor
mutation.
 For
each
suppressor,
indicate
if
it
would
be
an
informational
or
interaction
suppressor,
and
 if
it
is
gene
specific
or
non‐specific.
There
may
be
more
than
one
possible
answer.

 
 A
mutation
in
the
poly‐adenylation
signal
of
the
Ras
mRNA.
 
 
 
 
 
 A
mutation
in
EGF
that
disrupts
the
EGF‐receptor
binding
site
 
 
 
 
 A
point
mutation
in
the
ribosome
binding
site
of
the
EGF
mRNA
that
disrupts
the
 recruitment
of
ribosomes
to
the
mRNA
 
 
 
 
 7a.
Imagine
that
you
have
generated
a
transgenic
mouse
that
has
a
copy
of
the
gene
for
 green
fluorescent
protein
(GFP)
integrated
into
the
X
chromosome
(XGFP).
You
cross
a
 female
mouse
homozygous
for
the
GFP
transgene
with
a
wild‐type
male.
What
will
the
 pattern
of
GFP
expression
be
in
male
offspring?
 
 
 
 7b.
What
will
the
pattern
of
GFP
expression
be
in
female
offspring?
 
 
 
 
 7c.
Next
you
delete
the
Xist
locus
in
the
transgenic
mouse
and
repeat
the
cross
described
 above.
How,
if
at
all,
will
this
change
the
expression
of
GFP
in
the
F1
offspring?
 
 
 
 
 7d.
As
the
XGFPXGFP
female
mice
age,
some
of
them
develop
tumors.
You
isolate
the
cells
 from
the
tumor
of
one
mouse
and
find
that
100%
of
the
cells
are
green.
When
you
isolate
 cells
from
a
tumor
in
another
mouse
you
find
that
none
of
the
cells
are
green.
How
can
this
 be?

 
 
 
 8.
You
have
discovered
a
point
mutation
in
the
protease
caspase‐1
that
converts
a
cysteine
 (TGT)
codon
into
a
serine
(TCT)
codon
at
position
189.
Because
this
cysteine
normally
 forms
the
core
of
the
catalytic
site
in
caspase‐1,
the
point
mutant
has
lost
all
protease
 activity.
In
a
screen
for
suppressor
mutations
you
find
that
a
mutation
in
a
tRNA
can
 restore
caspase‐1
to
its
wild‐type
function.

 
 In
which
tRNA
would
you
expect
to
find
this
suppressor
mutation?
 
 
 
 Draw
the
base‐pairing
that
occurs
between
the
mRNA
of
caspase‐1
and
tRNAs
at
 position
189
in
a
wild‐type
background
vs.
a
suppressed
background.

 
 
 
 
 
 
 
 
 
 9.

You
perform
the
following
fly
cross:
w+/w‐

female
X

w+/Y
male.

 One
of
the
F1
females
is
white‐eyed.

Which
parent
underwent
a
meiotic
error?

In
which
 stage
of
meiosis
did
the
error
occur?
 
 ...
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This note was uploaded on 04/05/2010 for the course MCB 104 taught by Professor Urnov during the Spring '09 term at Berkeley.

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