3. Ch4_Sept_18_posted_no_questions_2_per

3. Ch4_Sept_18_posted_no_questions_2_per - 9/17/09

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 9/17/09 Chapter
4
–
The
Chromosome
Theory
of
 Inheritance
 
 (Mitosis
&
Meiosis) 
 REMINDER: You should have already bought & registered your clicker… Different
chromosomes
carry
different
genes 
 How many different chromosomes are in humans? A.  2 B.  23 C.  46 D.  I can’t count this early in the morning. 1 9/17/09 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. Homologous
chromosomes
carry
the
same

 genes,
but
may
have
different
alleles. 
 23
different
chromosomes… 
 So why 46 chromosomes? With love from Mom With love from Mom With love from Dad With love from Dad 2 9/17/09 FerHlized
 egg
 development
 adult
 To
have
this
process
happen
–
need
lots
&
 lots
of
cell
division
 Cell
Division
 Mitosis
 Meiosis
 • All organisms are made of cells • All cells come from pre-existing cells 3 9/17/09 Cell
Division
 Mitosis
 Meiosis
 Cell
Division
 Mitosis
 Meiosis
 Egg
 FerHlizaHon
 Sperm
 4 9/17/09 Ploidy
&
Basic
Chromosome
Number… 
 • Can describe organism by number of chromosomes in its gametes (n). • Haploid (n) • Diploid (2n) •  Number
of
chromosomes
in
a
 chromosome
set
(n)
depends
on
the
 species
 • Humans 
 
 
2n
=
46
 • Dogs 
 
 
 
2n
=
72
 • Fruit
fly 
 
 
2n
=
8
 • Chimpanzee 
 
2n
=48
 • Garden
pea 
 
2n
=
14
 •  Many
plants
have
more
than
2
sets
of
chromosomes
 (e.g.,
tetraploid)
 Ploidy
&
Basic
Chromosome
Number… 
 • Can describe organism by number of chromosomes in its gametes (n). • Also by the basic chromosome number (x). • Haploid (n) • Diploid (2n) •  Number
of
chromosomes
in
a
 chromosome
set
(n)
depends
on
the
 species
 • Humans 
 
 
2n
=
46
 • Dogs 
 
 
 
2n
=
72
 • Fruit
fly 
 
 
2n
=
8
 • Chimpanzee 
 
2n
=48
 • Garden
pea 
 
2n
=
14
 5 9/17/09 Cell
Cycle 
 Interphase – chromatin is uncondensed long thin strands Chromatin condenses in early part of mitosis or meiosis 23
different
chromosomes… 
 So why 46 chromosomes then? HOMOLOGUES!!! metacentric acrocentric 6 9/17/09 Homologous
Chromosomes 
 DNA
replicaHon
precedes
cell
division
 •  Sister
chromaHds
 

 
 

 Sister
 chromaHds
 
 

 7 9/17/09 ChromaHn
CondensaHon 
 Chromatin “condenses” Mitosis
vs
Meiosis 
 •  Mitosis

idenHcal
offspring

=
CLONES
 •  Homologues
don’t
interact
 •  1
nuclear
division
 8 9/17/09 Mitosis
vs.
Meiosis… 
 •  Meiosis
2
nuclear
divisions

 •  (MI
=
reducHonal
division;
MII
=
equaHonal
division)
 Independent
 assortment
is
 ONE
way
to
 create
 variaHon
 Mitosis
vs.
Meiosis… 
 •  Independent
Assortment
of
 chromosomes
(MI)
 Russell et al. 2007 9 9/17/09 Mitosis
vs.
Meiosis… 
 •  RecombinaHon
is
one
way
to
 create
variaHon
(MI)
 2n
=

#
of
different
combinaHons
 of
maternal
&
paternal
 chromosomes
 For
humans
____
combinaHons
 Mitosis
(asexual)
vs.
Meiosis
(sexual)… 
 •  FerHlizaHon
is
one
way
to
create
variaHon
 •  (restores
full
complement
of
chromosomes)
 Maternal origin Paternal origin 10 9/17/09 Mitosis
vs
Meiosis… 
 •  Mitosis

idenHcal
offspring

 •  Meiosis

maintains
variaHon
(helped
along
by
ferHlizaHon)
 •  Independent
assortment
 •  recombinaHon
 •  Reduces
the
number
of
chromosomes
 •  Only
1
homologue
of
each
chromosome
pair
into
daughter
 cell
 •  Only
occurs
in
specialized
Hssues
(gonads)
 •  Produces
specialized
cells
(gametes)

 •  These
parHcipate
in
ferHlizaHon
 Mitosis
vs
Meiosis… 
 MITOSIS MEIOSIS (not part of meiosis) (Not part of mitosis) 2 diploid daughter cells 4 haploid daughter cells 11 9/17/09 Mitosis
vs
Meiosis…the
rumble
begins… 
 What part of meiosis most closely resembles mitosis? Why? Draw other combinations of chromosomes that could occur… 12 9/17/09 DNA
replicaHon
preceded
cell
division 
 When do sister chromatids become separate chromosomes? Cell
Cycle 
 13 9/17/09 Sex
chromosomes 
 In humans – sex is genetically determined Sex
DeterminaHon 
 14 9/17/09 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
 Mistakes
in
Meiosis
 Aneuploid
gametes
can
result
 
(abnormal
#
of
chromosomes)
 15 9/17/09 Mistakes
in
Meiosis
 •  Chromosomes
may
not
be
properly
distributed
  MI
NondisjuncHon
=
failure
of
homologous
chromosomes
to
 separate
  MII
NondisjuncHon
=
failure
of
sister
chromaHds
to
separate

 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
geneHc
informaHon
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
(transcripHon)
generates
a
molecule
 (the
RNA
transcript)
that
becomes
a
messenger
RNA
(mRNA).
 •  Coded
informaHon
in
an
mRNA
is
translated
into
a
sequence
of
 amino
acids
in
a
polypepHde.
 •  MutaHons
can
alter
the
DNA
sequence
of
a
gene.
 •  The
geneHc
variability
created
by
mutaHon
is
the
basis
for
biological
 evoluHon.
 16 9/17/09 Mitosis
vs
Meiosis…how
much
DNA? 
 Snustad 2008 17 ...
View Full Document

Ask a homework question - tutors are online