Transcript Cell Division PPT

Cell
Reproduction
Unit
Chromosome Structure
- chromosome = a long
continuous thread of DNA that
consists of numerous genes
with regulatory information
coiled around proteins in
compact structures
Chromosome Structure
- DNA wraps around proteins
(called histones) to become
compact
Chromosome Formation
Chromosome Structure (cont)
Cell Cycle
= the regular pattern of
growth, DNA duplication,
and cell division that occurs
in cells
Cell Cycle
- results in two cells
(daughter cells) identical to
one another
- made up of 5 Phases
Cell Cycle (cont)
1) G1 Phase = cell growth
2) S Phase = DNA is copied
3) G2 Phase = cell prepares
for cell division
Together Phases 1-3 are
called Interphase
Cell Cycle (cont)
4) M Phase (Mitosis)
- division of the nucleus
5) C Phase (Cytokinesis)
- division of the cytoplasm
Cell Cycle (cont)
Sequence of the Cell Cycle
G1
S
G2
M
C
Cell Cycle (cont)
Cell Cycle (cont)
Mitosis
= division of the nucleus
and its contents
- discovered by Walther
Flemming in 1882
Phases
of
Mitosis
1) Prophase
- DNA coils to become
chromosomes
- nuclear membrane disappears
- microtubules called spindle
fibers grow from centrioles to
center of cell
1) Prophase (cont)
Spindle Fibers: 2 Types
1) Kinetochore Fibers –
attach to chromosomes (at
centromere)
2) Polar Fibers – spread
throughout cell
Prophase
Centrioles
Spindle
Fibers
Nucleus with
Chromosomes
Late Prophase
Kinetochore
Fibers
Polar
Fibers
2) Metaphase
- chromosomes line up
in center
Metaphase
3) Anaphase
- chromosomes pull
apart and move to
opposite sides of cell
Anaphase
4) Telophase
- chromosomes uncoil
- nuclear membrane reforms
Telophase
Chromosomes
Uncoil
New
Nuclear
Membrane
Forms
Phases of Mitosis
How do you remember
the order of the
phases of Mitosis?
Just remember this
phrase……….
PMAT
P = Prophae
M = Metaphase
A = Anaphase
T = Telophase
MATT
PEE
Cytokinesis
- cell membrane forms a
cleavage furrow and
cytoplasm divides
- in plants, a cell plate forms
between each cell
Cytokinesis
Cleavage
Furrow
Cell Plate
Regulation of Cell Division
- controlled by external and
internal factors
- External Factors
1) cell to cell contact
2) growth factors
Cell to Cell Contact
Regulation of Cell Division (cont)
Growth Factors – Examples
- Platelets
Regulation of Cell Division (cont)
Growth Factors – Examples
- Erythropoietin
(stimulates red
blood cell
production)
Regulation of Cell Division (cont)
- Internal Factors
- enzymes and proteins
released by the cell
Regulation of Cell Division (cont)
- apoptosis = programmed cell
death
Webbed
Fingers
Apoptosis – Leaves in Fall
Incomplete Apoptosis
Cancer cells form tumors that may
metastasize to other parts of the body
Normal Cell
Cancer Cell
Bloodstream
A healthy cell may
become a cancer
cell if certain
genes are
damaged
Cancer cells form tumors that may
metastasize to other parts of the body
Cancer cells
divide more often
than do healthy
cells and may
form disorganized
clumps called
tumors
Cancer cells form tumors that may
metastasize to other parts of the body
Sometimes
cancer cells break
away from the
tumor. They can
be carried in the
bloodstream to
other parts of the
body where they
form new tumors.
According to the American Cancer
Society, skin cancer is the most
common of all cancers.
This cancerous
mole is an
example of a
skin cancer,
which may
metastasize
quickly.
ABCD Rule (for moles, etc)
Mnemonic to help remember what to look for
A = Asymmetry (irregular shape)
B = Border is irregular shape
C= Color change (changing or many colors)
D = Dimension (1/4 in or less)
**other key signs to look for:
New growth, changes in growth, painful
feeling
Look for the ABCD Rule in this mole?
Why is sex with
someone else
better than sex by
yourself?
Asexual Reproduction
= reproduction of offspring
from one parent
- offspring are genetically
identical to the parent
…this is a BAD thing
Sexual Reproduction
= reproduction of offspring
from two parents
- offspring are genetically
different from the parents
…this is a GOOD thing
Example
Nut
Disease
in
Squirrels
Some eukaryotic cells divide by
mitosis
Some organisms can reproduce
by asexual or sexual reproduction
(depends on conditions)
Meiosis
Meiosis
= cell reproduction that
forms gametes (= sex
cells = egg/sperm)
Meiosis (cont)
- # of chromosomes is
halved
- produces haploid cells
(23 chromosomes)
Meiosis (cont)
Two Stages:
Meiosis I
Prophase I, Metaphase I,
Anaphase I, Telophase I
Meiosis II
Prophase II, Metaphase II,
Anaphase II, Telophase II
Meiosis (cont)
Homologous chromosomes line
up ( = tetrad)
Portions of chromatids are
exchanged ( = crossing over)
- results in new mixture of
genetic material ( = genetic
recombination)
Meiosis (cont)
Meiosis (cont)
Chromosomes separate
randomly ( = law of
independent assortment)
- results in genetic
variation
Meiosis (cont)
Spermatogenesis
= production of sperm
cells
- makes 4 haploid cells
called spermatids
Spermatogenesis
Oogenesis
= production of egg cells
- makes 1 haploid egg cell
and 3 polar bodies
- polar bodies degenerate
Oogenesis
Mitosis
Examples:
vs.
Meiosis
Examples: Mitosis vs. Meiosis
A human has 46 chromosomes
- after mitosis, each body cell
has 46 chromosomes
- after meiosis, each sex cell
(egg and sperm) has 23
chromosomes