4. Ch4_6_Review_of_Sept._16_18th

4. Ch4_6_Review_of_Sept._16_18th - 9/29/09

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Unformatted text preview: 9/29/09 Chapter
4
–
The
Chromosome
Theory
of
 Inheritance
 
 (Mitosis
&
Meiosis) 
 REMINDER: You should have already bought & registered your clicker… Different
chromosomes
carry
different
genes 
 The differences in staining between different pairs (e.g., between Chr 3 pair & Chr 17 pair) indicate differences in DNA sequence (indicative of different genes carried on different chromosomes)…thus chromosomes 3 and 17 carry different genes. Protein end product of gene expression 1 9/29/09 • Homologous
chromosomes
(e.g.,
the
green
 chromosomes
carry
the
same

genes,
but
 may
have
different
alleles.
 • Sister
chromaEds
are
duplicates
of
the
same
 homolog
–
thus,
same
genes
&
same
alleles
 (at
least
unEl
X.O.)
 • Non‐sister
chromaEds
are
from
homologous 
 chromosomes
–
thus,
same
genes,
&
 perhaps
different
alleles
 from Mom from Mom from Dad from Dad Which
of
the
following
describes
these
sister
chromaEds?
 A.  1
is
made
up
of
2
strands
of
original
DNA,
the
other
newly
synthesized
DNA.
 B.  Each
one
is
made
up
of
1
strand
original
DNA
&
1
strand
of
newly
synthesized
 DNA.
 C.  You
can’t
tell
from
this
picture.
 D.  Each
sister
chromaEd
is
made
up
of
old
DNA.
Its
homologue
is
made
up
of
the
 newly
synthesized
DNA.
 If
you
expose
a
culture
of
human
cells
to
3H‐thymidine
during
S
phase,
how
 would
the
radioacEvity
be
distributed
over
a
pair
of
homologous
chromosomes
 

 
 

 at
metaphase?
Would
the
radioacEvity
be
in

 A.  B.  C.  D.  E.  One
chromaEd
of
one
homolog.
 Both
chromaEds
of
one
homolog.
 One
chromaEd
each
of
both
homologs.
 Both
chromaEds
of
both
homologs.
 Some
other
paWern.
 Sister
 chromaEds
 

 
 

 2 9/29/09 Meiosis 
 •  Cells
produced
by
MI
have
just
1
copy
of
each
chromosome
 •  Cells
produced
by
MII
also
have
just
1
copy
of
each
chromosome,
but
the
 chromosomes
are
now
unreplicated
(b/c
the
sister
chromaEds
have
separated)
 •  Both
unreplicated
&
replicated
chromosomes
considered
single
chromosomes
 (even
though
a
replicated
chromosome
is
composed
of
2
sister
chromaEds)
 RecombinaEon
(Meiosis)… 
 •  RecombinaEon
is
one
way
to
 create
variaEon
(MI)
 3 9/29/09 •  Series
of
steps
in
Prophase
I
 RecombinaEon
(Meiosis)… 
 Mitosis
(asexual)
vs.
Meiosis
(sexual)… 
 •  FerElizaEon
is
one
way
to
create
variaEon
 •  (restores
full
complement
of
chromosomes)
 Maternal origin Paternal origin 4 9/29/09 Sexual
ReproducEon
&
GeneEc
VariaEon… 
 •  Sexual
reproducEon
=
producEon
of
offspring
through
fusion
of
 gametes
 •  Thus,
self‐ferElizaEon
IS
SEXUAL
reproducEon
 Black arrows represent fertilisation events b/w different gametes Sexual
ReproducEon
&
GeneEc
VariaEon… 
 •  Sexual
reproducEon
=
producEon
of
offspring
through
fusion
of
 gametes
 •  Why
is
sexual
reproducEon
useful?
 •  Shuffling
of
maternal
&
paternal
chromosomes
AND
X.O.
in
MI
 produce
UNIQUE
combos
of
alleles
 •  Offspring
of
asexual
reproducEon

gene)cally
iden)cal
to
 parent
&
each
other
=
CLONES
 •  Offspring
of
sexual
reproducEon

gene)cally
unique
 •  Different
from
mother;
different
from
father;
different
from
 siblings
(excepEon:
idenEcal
twins,
triplets,
etc…)
 5 9/29/09 Cell
Cycle 
 •  The
somaEc
cells
of
a
parEcular
male
organism
contain
only
1
pair
 of
homologous
chromosomes
(A1
and
A2)
and
1
addiEonal
 chromosome
without
a
homolog
(chromosome
Q).
Which
 chromosomal
combinaEons
would
be
likely
among
the
4
meioEc
 products
from
a
single
cell?
 A.  B.  C.  D.  A1Q,
A1Q,
A2,
A2
 A1Q,
A2Q,
A1,
A2
 A1Q,
A1Q,
A2Q,
A2Q
 A1A1,
A2A2,
Q,
Q
 6 9/29/09 Hybrid
Sterility 
 •  If
chromosomes
can’t
pair
 during
meiosis
I,
don’t
 segregate
properly
 •  May
be
b/c
diff
#
of
 chromosomes
in
gametes

 when
these
cells
go
to
make
 gametes
can’t
pair
up
 •  May
be
b/c
chromosomes
are
 too
dissimilar
 The
smushyfinned
fish
has
44
chromosomes
per
diploid
set,
while
the
 crown‐nosed
fish
has
50.

A
chance
maEng
between
a
male
 smushfinned
fish
&
a
female
crown‐nosed
fish
produced
1
offspring.


 How
many
chromosomes
were
observed
in
the
somaEc
cells
of
the
 offspring?
 Will
this
offspring
be
able
to
form
viable
(funcEoning)
gametes?
 
1.
Yes
 
2.
No
 7 9/29/09 Mistakes
in
Meiosis
 Aneuploid
gametes
can
result
 
(abnormal
#
of
chromosomes)
 Mistakes
in
Meiosis
 •  Chromosomes
may
not
be
properly
distributed
  MI
NondisjuncEon
=
failure
of
homologous
chromosomes
to
 separate
  MII
NondisjuncEon
=
failure
of
sister
chromaEds
to
separate

 8 9/29/09 Chapter
6
–
DNA
Stuff 
 •  When
DNA
replicates,
each
strand
of
a
duplex
molecule
serves
as
 the
template
for
the
synthesis
of
a
complementary
strand.
 •  When
geneEc
informaEon
is
expressed,
one
strand
of
a
gene’s
DNA
 duplex
is
used
as
a
template
for
the
synthesis
of
a
complementary
 strand
of
RNA.
 •  For
most
genes,
RNA
synthesis
(transcripEon)
generates
a
molecule
 (the
RNA
transcript)
that
becomes
a
messenger
RNA
(mRNA).
 •  Coded
informaEon
in
an
mRNA
is
translated
into
a
sequence
of
 amino
acids
in
a
polypepEde.
 •  MutaEons
can
alter
the
DNA
sequence
of
a
gene.
 •  The
geneEc
variability
created
by
mutaEon
is
the
basis
for
biological
 evoluEon.
 Mitosis
vs
Meiosis…how
much
DNA? 
 Snustad 2008 9 9/29/09 Assume
that
a
human
somaEc
(non‐sex)
cell
contains
~
13
 picograms
of
DNA
in
the
G1
phase.
How
many
picograms
of
 DNA
(c)
are
expected
in
a
gamete
produced
by
this
 individual?
 A.  B.  C.  D.  6.5
 13
 26
 52
 

 
 

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