Download Cell Reproduction & Mitosis

 Role
of

DNA



1. Info. In DNA must be present in
each cell after division
2. Stores info for which proteins to
make and when
3. Directs cell activities
4. DNA gets copied and redistributed
during division
 Role
of
DNA

A single chromosome contains
thousands of genes that code for
proteins involved in determining how a
person’s body develops and function
 Pro
vs.

Eu
 How
many
chromoso
mes do
we have?

1. What is the main
difference between
Prokaryotic and Eukaryotic
organisms?
2. How does cell
reproduction occur in
prokaryotic organisms?
3. Where does cell
reproduction occur in
eukaryotic organisms?

 Chromo-
somes
 1.
Each human somatic (body)
cell has 23 pairs of
chromosomes ( = 46 total
chromosomes)
 Chromosomes differ in size,
shape
 Contain thousands of genes that
determine how the body
functions and develops
 Chromo-
somes
 2.
Homologous chromosomesEach 23 pairs of chromosomes
consists of 2 homologues
 Similar in size, shape and
genetic content (chromatids
that are connected)
 Chromo-
somes
 3.
One half of each
chromosome pair comes from
the mother and the other half
from the father
 Chromo-
somes
A
somatic cell, that contains 2
sets of chromosomes is diploid
 Gametes (sex cells) only have 1
set of chromosomes - haploid
 Zygote - a fertilized egg cell
 We use the symbol “n” to
represent one set of
chromosomes
 Chromosome
 Haploid
numbers in common species
and Diploid Chromosome
Numbers
 Autosomes
 22
of the chromosome pairs in
humans are called autosomes not directly involved in
determining the gender of an
individual
 Sex
Chromosom
es

One of the chromosome pairs
containing genes that determine
the sex of the individual
• X and Y
• XX - female
• XY- male
• The sex is determined by the male
 Changes
chromosome
number
in
 1.
Presence of all 46
chromosomes is essential for
normal development and
function
 2. Humans missing one
chromosome typically do not
survive
 Changes
in
chromosome
number
 Can
detect
this in
Karyotype
 3.
More than two copies of a
chromosome - trisomy
(improper development occurs)
 Ex: Down Syndrome (21)
 Non-

disjunction


When chromosomes don’t separate
properly when egg and sperm form
One gamete ends up with both
chromosomes, the other has none
Trisomy results when abnormal
gamete fuses with another
 How
many chromosomes do humans
have? How many pairs?
 What
is the difference between “haploid”
and “diploid”?
 Give
the sex chromosomes for females &
males
 Why
is it essential to have all 46
chromosomes?
 Draw
a pair of homologues, draw a gene
on one of the homologues, and label the
chromatids
 Change
in
chromosome
structure
 MUTATION
- change in
chromosome structure (4
TYPES)
 Change
in
chromosome
structure
 1.
Deletion- piece of
chromosome completely breaks
off (often fatal)
 Change
in
chromosome
structure
 2.
Duplication- chromosome
fragment attaches to its
homologue (doubles the info - 2
copies of a gene)
 Change
in
chromosome
structure
 3.
Inversion- chromosome
piece reattaches to original
chromosome in reverse
orientation
 Change
in
chromosom
e structure
 4.
Translocation- chromosome
piece attaches to nonhomologous chromosome
All
of the four mutations
discussed could prove
fatal for the individual
 Cell
Cycle
 Repeating
sequence of growth
and division in the life of an
organism
 Cell
Cycle
A
cell spends 90% of its time in
the first three phases – called
Interphase
• G1
• S
• G2
 Cell
Cycle
 G1-
First Growth Phase
• Rapid cell growth and development,
routine functions
• Major part of cell life spent here
• Non-dividing cells remain here
• Muscle cells and nerve cells always
here, cannot be replaced
 Cell
Cycle
 S-
Synthesis phase
• DNA copied, end up with sister
chromatid
 Cell
Cycle
 G2-
Second Growth Phase
• Cell prepares nucleus to divide
• Microtubules assembled for moving
chromosomes during mitosis
 Cell
Cycle
 Mitosis-
nucleus divides into two
• Each nucleus ends up with same
type and number of chromosomes
• Allows organisms to:
 Grow
 Replace damaged tissue
 Asexually reproduce
 Cell
Cycle
 Cytokinesis-
half
cytoplasm divides in
 Control
of
the cell cycle
 1.
Cell growth checkpoint (G1)
decides whether the cell will
divide
• A. Cell must be healthy and large
enough first
• B. Proteins will stimulate transition
to S phase
 Control
of
the cell cycle
 1.
Cell growth checkpoint (G1)
decides whether the cell will
divide
• C. If conditions are unfavorable or
cells need a rest, growth will stop
here
• D. Nerve and muscle cells remain
here forever
 Control
of
the cell cycle
 2.
DNA synthesis G2
checkpoint- DNA repair enzymes
check the DNA replication
• A. Once past this point, proteins
trigger mitosis
 Control
of
the cell cycle
 3.
Mitosis checkpoint- triggers
end of mitosis
• Signals beginning or G1 phase
again
 Losing
Control of
the cell cycle

Cancer- uncontrolled growth of
cells caused by:
• A. Mutagens- readily damage DNA
(pollutants, radiation, other
environmental factors)
• B. When gene coding for proteins that
regulate cell cycle are mutated
 Losing
Control of
the cell cycle
 Cancer-
uncontrolled growth of
cells caused by:
• C. When growth promoting proteins
are mutated and actually speed up
the rate of cancer
 Oncogenes- accelerate rate of cell
division
 Losing
Control of
the cell cycle

Cancer- uncontrolled growth of cells
caused by:
• D.
When mutations inactivate the control
proteins that normally slow/stop cell cycle
 Tumor Suppressor Genes- releases the
“brakes” on cell division
 Differentiate
between the G1, G2 and S
phases of the eukaryotic cell cycle
 Relate what occurs at each of the three
principal checkpoints in the cell cycle
 Why are individual chromosomes more
difficult to see during interphase than
during mitosis?
 Mitosis:
Spindles

Made of centrioles and microtubule
fibers that move chromosomes during
cell division
• A. Extra set made right before division
• B. Travel to opposite ends of cell
• C. Only animal cells have centrioles
• D. Animals and plant cells both have
spindle fibers
 Mitosis:
Spindles




E. Microtubules attach to cell poles
and chromosome centromeres
F. Chromosomes begin to move
towards opposite ends of cell
G. Spindle fibers reel in the attached
chromosomes as the ends of the
fibers at the poles are broken down
H. Each pole gets a full set of
chromosomes
46 X’s
92 X’s
Fertilized
Cell
Chromosomes
copied
46
X’s
46
X’s
46
X’s
46
X’s
 Mitosis:
Stages

1. PROPHASE
• Chromosomes uncoil, become visible
• Nuclear envelope disappears
• Spindle forms
 Mitosis:
Stages

2. METAPHASE
• Chromosomes move to center of cell and
attach to spindle fibers along equator
 Mitosis:
Stages

3. ANAPHASE
• Centromeres divide
• Sister chromatids split and move to
opposite poles as spindle fibers shorten
 Mitosis:
Stages

4. TELOPHASE
• Nuclear envelope reforms
• Chromosomes recoil
• Spindle and fibers break down
 Mitosis:
Stages

5. CYTOKINESIS
• Cytoplasm divided in half, cell membrane
reforms
• Animal: cell pinches in half by belt of
protein
• Plant: vesicles from golgi line down middle
of cell to make a cell plate
 New cell wall grows on either side of plate
 Plate breaks cell into two
 Mitosis:
An Interactive Animation
 Molecular
Expressions Cell Biology:
Mitosis Interactive Java Tutorial
 Home(page)
Movies - QT and Flash to illustrat...
 Dr Chromo's school: mitosis
 Molecular Expressions Photo Gallery: Mitosis
 Mitosis
 The Cell Cycle & Mitosis Tutorial
 Mitosis: An Interactive Animation
 Describe
the function of the microtubules
during anaphase
 Describe the events that occur during each
of the four stages of mitosis
 Compare how cytokinesis occurs in plant
cells and how it occurs in animal cells