Download Cell Growth and Reproduction

Mitosis
The Cell Theory
• All living things are made up of one or more
cells
• Cells are the basic unit of structure and
function in living things
• All cells come from preexisting cells
Section Summary
• The genetic material is
deoxyribonucleic acid (DNA).
• DNA is packaged into
chromatin, which
condenses to form
chromosomes.
Section Summary
• During interphase of the cell cycle, the cell
lives, grows, and replicates its DNA.
• In mitotic phase (M phase), the
chromosomes distribute to daughter cells.
• A duplicated chromosome consists of two
sister chromatids.
Human Karyotype
Chromosome numbers
Agrodiaetus
butterfly
268
Alfalfa
32
Aquatic Rat
92
Jack jumper ant
2
American Badger
32
American Black Bear 74
Kamraj (fern)
94
Kangaroo
16
Koala
Lion
16
38
Maize
20
Mango
40
Meerkat
Mosquito
36
6
Mouse
40
This insect has one of the highest chromosome numbers
among all animals.
Cultivated alfalfa is tetraploid, with 2n=32. Wild relatives
have 2n=16.
Previously thought to be the highest number in mammals,
tied with Ichthyomys pittieri.
2 for females, males are haploid and thus have 1;
smallest number possible.
http://www.oocities.org/ganmni/
Genes
• Every cell’s DNA is organized into genes.
• Genes are units of inherited information
that carry a code for specific traits or
functions.
Genes
• Many genes code for proteins.
• The information contained in genes is
responsible for inheritance — the passing
down of traits from parent organisms to
their offspring.
DNA
• The nucleus contains the cell’s DNA.
• For much of a cell’s life, its DNA exists as a
mass of very long fibres called chromatin, a
combination of DNA and protein.
• Chromatin is very thin and not usually
visible with a
light microscope.
Chromosomes
• As a cell is preparing to divide, its
chromatin fibres condense, becoming
visible compact structures called
chromosomes.
Chromosomes
• A chromosome consists of one long,
condensed DNA molecule containing
hundreds or thousands of genes.
Chromosome
Chromatin
The Components of DNA
DNA consists of a long chain of
subunits called nucleotides.
A nucleotide has three parts:
1. A ring-shaped sugar called deoxyribose
2. A phosphate group
3. A nitrogenous base (or base, for short): a
single or double ring of carbon and nitrogen
atoms
DNA limits cell size
• Nucleus contains blueprints for cell
proteins
• Proteins used by almost all organelles to
function
DNA limits cell size
• There is a limit of how quickly proteins
can be copied and made in nucleus
• Cell cannot survive unless DNA can
support protein needs of cell
Cell Cycle
• Cell Cycle: Sequence of growth and
division of the cell.
Phases of Cell Cycle
• INTERPHASE:
– The longest phase
– Cell grows in size
– Cell carries on
metabolism
– Chromosomes are
duplicated to prepare
for division
Phases of the Cell Cycle
• After Interphase, cell enters period of
division, called Mitosis.
Mitosis:
• Forms two identical daughter cells each
with a complete set of chromosomes
Mitosis
Phases of Mitosis
Four phases:
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase
•
•
•
•
chromosomes condense
nucleolus and nuclear envelope disintegrates
centrioles migrate to opposite ends
spindles form between centrioles
Prophase
Chromosome
Long stringy chromatin coils up
into visible chromosomes
Chromatin
Prophase
• Each duplicated chromosome is made of
two halves called sister chromatids.
• Sister chromatids are held together by a
centromere
Centromere
Sister
chromatids
Prophase
Spindle fibers
Disappearing
nuclear envelope
Double stranded
chromosome
Metaphase
• Double stranded chromosomes attach to
spindle fibers by centromeres
• Double stranded chromosomes pulled by
spindle fibers and line up on equator
Metaphase
• This arrangement of the chromatids
ensures that each new cell receives
identical and complete set of chromosomes
Anaphase
• Centromeres split
• Sister chromatids separate
• Shortening of spindle fibers pull apart
chromatids to opposite poles
Telophase
• Begins once chromatids reach opposite poles
• Chromosomes begin to unwind
• Spindle breaks down
Telophase
• Nucleolus and nuclear envelope reappears
around new set of chromosomes
• Two identical daughter cells formed
Cytokinesis
• After Telophase, the cell’s cytoplasm
divides.
• Animal Cells: the plasma membrane
pinches together, forming two separate
cells.
• Plant Cells: Cell plate laid across cell’s
equator—there is no pinching off. Cell
membrane forms around each cell and new
cell walls form on each side of cell plate
Cytokinesis
What are the results of Mitosis?
• Two identical daughter cells
– Single celled organism remains a single cell but
has replicated itself
– Multicellular organisms have grown or created
another cell that will work together as tissue to
perform a certain function
Mitosis Animation
CellsAlive
Cell Growth and Reproduction
Section Quiz:
1.
The stringy structures in the cell nucleus that
contain DNA are __________.
a.
b.
c.
d.
Centromeres
Chromatin
Genes
Chlorophylls
Cell Growth and Reproduction
Section Quiz:
2. What phases are the following cells in?
Cell Growth and Reproduction
TELOPHASE
Cell Growth and Reproduction
PROPHASE
Cell Growth and Reproduction
METAPHASE
Cell Growth and Reproduction
ANAPHASE
Cell Growth and Reproduction
CYTOKINESIS
Cell Growth and Reproduction
INTERPHASE
Control of the Cell Cycle
•
What happens when MITOSIS goes WILD?
– CANCER
Control of the Cell Cycle
• Cancer:
–
–
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Malignant growth due to
uncontrolled cell division
Caused by
environmental factors
Changes in enzyme
production
Figure
1
Lung cancer cells (530x). These cells are
from a tumor located in the alveolus (air sac)
of a lung.
Cancer
•
•
Cancerous cells form masses of tissues
called MALIGNANT tumors.
Tumors starve normal cells from nutrients
•
Wait! But can’t I have a BENIGN tumor?
–
–
YES! Benign tumors are masses of tissues that
are harmless. (BENIGN = HARMLESS)
Created by slower growing cells that clump
together to form lump
Control of the Cell Cycle
•
Can I prevent Cancer?
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Diets high in fiber and low in fat
Take vitamins
Daily exercise
Refrain from smoking and use of other tobacco
products
Avoid exposure to UV light (in sunlight)
Avoid exposure to X-rays