Download DNA → mRNA → Protein

DNA 
mRNA  Protein
transcription
translation
DNA 
mRNA  Protein
transcription
Chromosome
translation
Organization of DNA into Chromosomes
allows for orderlyy p
process of nuclear
functions such as
Molecular Level
{
Organization of DNA into Chromosomes
allows for orderlyy p
process of nuclear
functions such as
Molecular Level
{
DNA transcription
DNA replication
DNA repair
etc
etc.
Organization of DNA into Chromosomes
allows for orderlyy p
process of nuclear
functions such as
Molecular Level
{
Cellular Level
{
DNA transcription
DNA replication
DNA repair
etc
etc.
Organization of DNA into Chromosomes
allows for orderlyy p
process of nuclear
functions such as
Molecular Level
Cellular Level
{
DNA transcription
DNA replication
DNA repair
etc
etc.
{
Nuclear vs. Cytoplasmic organization
Chromosome duplication
Chromosome separation
Cell Division
etc.
Organization of DNA into Chromosomes
allows for orderlyy p
process of nuclear
functions such as
Molecular Level
Cellular Level
{
DNA transcription
DNA replication
DNA repair
etc
etc.
{
Nuclear vs. Cytoplasmic organization
Chromosome duplication
Chromosome separation
Cell Division
etc.
{
Reproduction
Evolution
Polyploidization
etc.
Organizmal Level
C t
Cytogenetics
ti = The study of
chromosome number, structure,
function, and behavior in relation to
gene inheritance, organization and
expression
i
Chromosome
Chromo = colored in response to dye
Some = body
Chromosome off Eukaryotes
Ch
E k
t have
h
been
b
the
th ttraditional
diti l
subject for cytogenetic analysis because they are large
enough to be examined with light microscope
History of cytogenetics
~1600
Janssen & Janssen, father & son lay claim to the invention of the
compound microscope
Soon after cellular structure of plants and animals were recognized
Significant improvements in
glass quality & lens
manufacturing lead to
Recognition of separate organelles within cells
History of cytogenetics
~1600
Janssen & Janssen, father & son lay claim to the invention of the
compound microscope
Soon after cellular structure of plants and animals were recognized
Significant improvements in
glass quality & lens
manufacturing lead to
Recognition of separate organelles within cells
Cell theory:
History of cytogenetics
~1600
Janssen & Janssen, father & son lay claim to the invention of the
compound microscope
Soon after cellular structure of plants and animals were recognized
Significant improvements in
glass quality & lens
manufacturing lead to
Recognition of separate organelles within cells
Cell theory:
Cells and their nuclei were the
basic units of structure and
function in living organisms
History of cytogenetics
~1600
Janssen & Janssen, father & son lay claim to the invention of the
compound microscope
Soon after cellular structure of plants and animals were recognized
Significant improvements in
glass quality & lens
manufacturing lead to
Recognition of separate organelles within cells
Cell theory:
Lineage theory:
Cells and their nuclei were the
basic units of structure and
function in living organisms
History of cytogenetics
~1600
Janssen & Janssen, father & son lay claim to the invention of the
compound microscope
Soon after cellular structure of plants and animals were recognized
Significant improvements in
glass quality & lens
manufacturing lead to
Recognition of separate organelles within cells
Cell theory:
Lineage theory:
Cells and their nuclei were the
basic units of structure and
function in living organisms
Cells are derived from preexisting
i ti cells
ll (i.e.
(i all
ll cells
ll
trace back to one original cell)
End of 19th century
Mitotic and meiotic cell division & sexual reproduction had been
described
Chromosomes had also been observed consistency of appearance
suggested
t d an important
i
t t basic
b i function
f ti
End of 19th century
Mitotic and meiotic cell division & sexual reproduction had been
described
Chromosomes had also been observed consistency of appearance
suggested
t d an important
i
t t basic
b i function
f ti
Early 1900: Age of Genetics
Mandel’s Laws are re-discovered
Genes are the basic unit of inheritance
e es are
a e different
d e e forms
o s of
o thee same
sa e gene
ge e that
a segregate
seg ega e during
du g
• Alleles
gamete formation (Law of Segregation)
• Alleles of different genes segregate independently (Law of
independent assortment)
End of 19th century
Mitotic and meiotic cell division & sexual reproduction had been
described
Chromosomes had also been observed consistency of appearance
suggested
t d an important
i
t t basic
b i function
f ti
Early 1900: Age of Genetics
Mandel’s Laws are re-discovered
Genes are the basic unit of inheritance
e es are
a e different
d e e forms
o s of
o thee same
sa e gene
ge e that
a segregate
seg ega e during
du g
• Alleles
gamete formation (Law of Segregation)
• Alleles of different genes segregate independently (Law of
independent assortment)
Chromosome
theory of heredity:
Heredity characters are carried & passed on to
generations in discrete units (Correlation between
Mendelian inheritance and chromosome behavior)
1920s and 1930s
Natural or irradiation induced alterations in chromosome number and
structure were observed. This lead to parallel studies of genetics and
cytogenetics.
Gene expression was observed (Lampbrush chromosomes)
1920s and 1930s
Natural or irradiation induced alterations in chromosome number and
structure were observed. This lead to parallel studies of genetics and
cytogenetics.
Gene expression was observed (Lampbrush chromosomes)
Recent history (Age of Molecular Cytogenetics)
Gene localization (in situ)
Details of chromosome structure
Studies of genomes (FISH and GISH)
Role of various chromosome regions is realized
Artificial chromosomes are made
Single chromosomes are purified
etc.
Future
?
Tools of Cytogenetics
Light microscope
manipulating
i l ti the
th path
th off light
li ht thru
th optics
ti
E i
Eyepiece
Tube
Revolving nosepiece
Objective Lenses
Specimen Stage
Iris control
Condenser lever
Condenser centering
Focus control
Condenser
Filters
Auxiliary lens
Iris diaphragm
Illumination
Tools of Cytogenetics
Light microscope
manipulating
i l ti the
th path
th off light
li ht thru
th optics
ti
Important factors
•optics
•wavelength of light
•liquid
q
immersion
•phase contrast
•fluorescence
•computer enhancement
Transmitting electron, Scanning electron and
Scanning tunneling microscopy have all
increased the power of observation
Glossary of terms
Cytogenetics = The study of chromosome number, structure,
function and behavior in relations to gene inheritance,
organization and expression
Chromosome= A structure composed of DNA and proteins
Chromosome
that bears part of the genetic information of the cell
Mitosis= A process of cell division in Eukaryotic cells by
which two daughter cells are formed
Meiosis= A two stage type of cell division in sexually
reproducing organisms that results in gametes with half the
chromosome number of the original cell
The Somatic Cell Cycle
Maternal
chromosome
Diploid Zygote
MITOSIS
Paternal
Diploid Zygote chromosome
MITOSIS
Maternal
chromosome
Diploid organism
Paternal
chromosome
Diploid organism
The Somatic Cell Cycle
Stages of the cell cycle:
 M Mitosis= period of cell division
Interpphase
 G1 Gap1=period
period during cellular interphase
from the end of one telophase to the
beginning of DNA replication
 S Synthesis=period of pre-mitotic
interphase when DNA is replicated
 G2 Gap2=period during interphase after
completion of DNA replication and before
beginning of prophase
G1 and G2 are called gaps in the cell cycle when
no DNA synthesis occurs
Cytological observations of the cell cycle are
divided into two parts, interphase and mitosis
The Somatic Cell Cycle
Mitosis
G2 Phase
Cell
division
Interphase
S Phase
G0 Phase
G1 Phase
The Mitotic cell cycle is essential
to cell division and growth of an
organism
The Mitotic cell cycle is essential
to cell division and growth of an
organism
Gene Expression and Cell Division conflict:
The Mitotic cell cycle is essential
to cell division and growth of an
organism
Gene Expression and Cell Division conflict:
 Gene expression requires that chromosomal
DNA bbe uncoiled
il d tto allow
ll access to
t enzymes
such as RNA polymerase
The Mitotic cell cycle is essential
to cell division and growth of an
organism
Gene Expression and Cell Division conflict:
 Gene expression requires that chromosomal
DNA bbe uncoiled
il d tto allow
ll access to
t enzymes
such as RNA polymerase
 Cell division requires that chromosomes be
tightly coiled to allow orderly migration of
chromosomes to daughter cells
The Mitotic cell cycle is essential
to cell division and growth of an
organism
Gene Expression and Cell Division conflict:
 Gene expression requires that chromosomal
DNA bbe uncoiled
il d tto allow
ll access to
t enzymes
such as RNA polymerase
 Cell division requires that chromosomes be
tightly coiled to allow orderly migration of
chromosomes to daughter cells
Gene Expression and Cell Division are
separated into different stages
The Somatic Cell Cycle
Mitosis
G2 Phase
Cell
division
Interphase
S Phase
G0 Phase
G1 Phase
Interphase
G1
1. Period of gene expression
2. Daughter cells retain the diploid set of
chromosomes and DNA content is 2c
3. More variable in length than S, G2 or M
4. Some event duringg G1 is the focus of
regulation of cell reproduction in tissues
5. Differentiated cells that cease to reproduce
usually contain G1 amount of DNA (2c)
whether cessation is reversible or
irreversible (G0)
Interphase
G1
6 In cells that continue to reproduce,
6.
reproduce the
reproductive rate is governed by the
average length of time that cells are
retained in the G1
7. Measurement of DNA content in dormant
plant embryos indicate cells are arrested in
G1
8. G1 may be absent in rapidly proliferating
cells of higher organisms, particularly
during embryogenesis
9. Once cells progress from G1 to S, they are
committed to proceed through mitosis
Interphase
S
1. Period of DNA synthesis (DNA content
goes from 2c to 4c)
2 Autoradiography shows that DNA synthesis
2.
is confined to a relatively short period
3. DNA replication is initiated by factors in
th cytoplasm
the
t l
a) when two or more nuclei share the same
cytoplasm,
y p
theyy are nearly
y always
y
synchronized
Interphase
S
4 DNA replication
4.
li i iis initiated
i i i d by
b factors
f
in
i the
h
cytoplasm
b) Gurdon (1973) observed that DNA
synthesis was initiated when nuclei from
various tissue of Xenopus were
implanted into an unfertilized egg
c) Nuclei from adult liver, brain, and blood
cells
ll injected
i j t d into
i t mature
t
eggs off
Xenopus initiated DNA synthesis within
90 minutes of injection
d) Inhibition of protein synthesis in G1 will
inhibit or delay on set of the S phase
Interphase
G2
1 The nucleus contains two diploid sets of
1.
chromatids (DNA content is 4c)
2. Period required for cells to synthesize
elements
l
t necessary for
f chromosome
h
condensation and the construction and
operation of the mitotic apparatus
3. Protein synthesis is necessary for cells to
complete most of the G2 period, but protein
synthesis required for mitosis is completed
prior to prophase
4. G2 lasts until mitosis begins
Interphase
G2
5 The fusion of a mitotic HeLa cell with an
5.
interphase cell results in condensation of
interphase chromosomes (Rao and Johnson,
1970))
a) Chromosomes do not have to be
replicated to respond to the
condensation signal
b) The condensation factor is effective
across phylogenetic lines (Bull sperm,
chicken erythrocytes, and mosquito
were condensed by the HeLa factor)
Life cycle of a sexually reproducing organism
correlated with the amount of DNA per cell
Fertilization
Mitotic divisions
Am
mount of D
DNA/cell C values
S A
4
S A
Meiotic divisions
S A1
3
Z
C
C
A2
2
G
G
1
0
Sequence of stages
G Gamete,
G=
Gamete Z
Z=Zygote
Zygote, S
S=Period
Period of DNA synthesis
synthesis,
A=Mitotic Anaphase, C=Somatic Cells, A1=First meiotic
anaphase, A2= Second meiotic anaphase
Mitosis
A mechanism by which replicated chromosomes
are evenly distributed to two daughter cells.
Each of the daughter cells will have the same
number and kind of chromosomes as the parent.
Stages of mitosis:
 Interphase
p
 Prophase
 Prometaphase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis
Stages of Mitosis
Interphase:
 Chromosomes are fine diffuse strands and
are difficult to see with light microscopy
 Chromosomes are duplicated
 The nuclear envelope is intact
Interphase
Stages of Mitosis
Interphase:
 Chromosomes are fine diffuse strands and
are difficult to see with light microscopy
 Chromosomes are duplicated
 The nuclear envelope is intact
Prophase
 Chromosomes condense into distinct
structures
 Chromosomes become visible with light
microscopy
Prophase
Stages of Mitosis
Interphase:
 Chromosomes are fine diffuse strands and
are difficult to see with light microscopy
 Chromosomes are duplicated
 The nuclear envelope is intact
Prophase
 Chromosomes condense into distinct
structures
 Chromosomes become visible with light
microscopy
Prometaphase
 Further chromosome condensation
 Nuclear envelope disintegrates
 Chromosomes become associated with
spindle
i dl apparatus
 Sister chromatids remain attached at the
centromere, but begin to separate at other
regions
Interphase
Prophase
Prometaphase
Prometaphase
Stages of Mitosis
M
Metaphase
h
Sister chromatid pairs are aligned near the
spindle with centromeres still associated
The centromeres orient toward opposite pools
and are lined up on the metaphase plate
Metaphase
Interphase
Prophase
Prometaphase
P
Prometaphase
t h
Metaphase
Stages of Mitosis
M
Metaphase
h
Sister chromatid pairs are aligned near the
spindle with centromeres still associated
The centromeres orient toward opposite pools
and are lined up on the metaphase plate
Anaphase
p
Sister chromatid pairs separate with one
member of each pair moving toward the poles
Anaphase
Anaphase
Stages of Mitosis
M
Metaphase
h
Sister chromatid pairs are aligned near the
spindle with centromeres still associated
The centromeres orient toward opposite pools
and are lined up on the metaphase plate
Anaphase
p
Sister chromatid pairs separate with one
member of each pair moving toward the poles
Telophase
Chromatids reach opposite poles and poleward
movement ceases
New nuclear envelope is formed around each
diploid chromosome set
Chromosomes begin to decondense
Anaphase
Anaphase
Telophase
Telophase
Stages of Mitosis
Cytokinesis
During

i mitosis
i i doubling
d bli off all
ll the
h cytoplasmic
l
i
organelles also occurs, they are distributed to
daughter cells during this stage
Central ring of myosin and actin fibers contract
to separate the daughter cells
In plants the cell plate is laid down in
preparation for the rigid cell wall
C t ki i
Cytokinesis
Anaphase
Anaphase
Telophase
Cytokinesis
Cytokinesis
Mitotic Index =
# of mitotic cells
Total # of cells
Mitotic cells = cells in stages from
prophase to telophase
Control of Mitotic Cell
Di i i
Division
G2 Phase
signal
i
l for
f G2 to
t
mitosis transition
S Phase
M Phase
G1 Phase
start signal
Molecular
clock
Control of Mitotic Cell
Di i i
Division
a)) The onset of mitosis is accompanied
p
by
y
the presence of an active maturation (or
mitosis) promoting factor (MPF)
Control of Mitotic Cell
Di i i
Division
 The onset of mitosis is accompanied
p
by
y
the presence of an active maturation (or
mitosis) promoting factor (MPF)
 MPF purified from frog eggs consists of
two protein subunits (Lohka et al. 1988).
These were recognized as the 34 kD
Protein Kinase (P34cdc2) and 45 kD Btype cyclin.
 Active MPF triggers the onset of mitosis,
immediately afterward following events
occur:
a)) Cyclin
y
activityy is degraded
g
b) The nuclear membrane begins to
break down
c)) Chromosome condensation begins
g
d) The spindle apparatus is organized
Phosphates
block active site
Inactive
P
P
Dephosphorylation
P
Phosphhorylation
G2
S
active site
M
G1
Breakdown of
Cyclin B
Cyclin B
Buildup of
Cyclin B
Inactive
P34
cdc2
(Protein kinase)
= MPF or maturation-promoting factor or mitosis
promoting factor
Glossary of terms
The Somatic Cell Cycle= Events that occur from one cell
division to the next
2C= DNA content of nucleus in the somatic cells of an organism
Chromatid= A single chromosomal strand; a metaphase
chromosome is composed of two “sister” chromatids
Centromere=A region of chromosome from which kinetichore
microtubules radiate during mitosis or meiosis
Kinetochore= A specialized region on the centromere that links
each sister chromatid to the mitotic spindle
Heterochromatin= non-transcribed
non transcribed eukaryotic chromatin that is
so highly compacted that it is visible with a light microscope
during interphase
Euchromatin The more open,
Euchromatin=
open unraveled form of eukaryotic
chromatin, which is available for transcription