Transcript Mitosis - Barrington 220

What is the most important part of
a cell when it wants to divide?
What important “stuff” is inside the nucleus?
What role does DNA play in our cells?
It tells your cell how to act and
what to become
What is DNA made up of?
Nucleic Acid
What does DNA look Like?
DNA looks like spaghetti in the cell
In this form it is called chromatin
• DNA can wind up on itself to form
chromosomes
– 46 chromosomes in human cells
Human Karyotype
Human Karyotype
• Shows many chromosomes are present
• Shows chromosomes with their pair
• One from mom and one from dad
• Also can identify gender
• Y Chromosomes are much smaller
• XX = female (two long chromosomes)
• XY = male (1 short and 1 long
chromosome)
• Can use karyotypes to identify
chromosomal abnormalities (trisomy 21)
Chromosome Parts
Single stranded
chromosome
Double stranded chromosome –
It has gone through DNA replication
Sister
chromatids
(identical
copies)
Why Do Cells Reproduce?
• To make new cells in order to grow and
repair itself
Cell Cycle
• A repeating process of cell growth and
division
CELL CYCLE
• Interphase
– A cell spends 90% of it’s life in interphase.
3 Phases of Interphase
G1- First
growth
phase
S phaseDNA
copied
G2Second
growth
phase
Mitosis (M) Phase
The nucleus and DNA
divide
Mitosis is divided into
phases:
Prophase
Metaphase
Anaphase
Telophase
What Cell Parts Are Involved?
Nuclear Membrane
Cytoplasm
Nucleus
Chromosomes
(DNA)
Cell Membrane
Centrioles
Nuclear
Membrane
Prophase
Centriole
Chromosomes
Spindle
Fibers
Prophase
Chromosomes thicken
Nuclear membrane begins to disappear
Spindle fibers start to form between the
centrioles
Metaphase
Centriole
Chromosomes
Spindle
Fibers
Metaphase
Chromosomes line up across middle
Spindle fibers are attached to each
chromosome (at the centromere)
Anaphase
Centriole
Chromosomes
Spindle
Fibers
Anaphase
Centromeres divide
Sister chromatids are pulled toward
opposite ends of the cell
Nuclear
Membrane
Telophase
Centriole
Chromosomes
Furrowing
Telophase
Nuclear membrane begins to re-form
Chromosomes uncoil (becoming less
visible)
Furrowing occurs
Cytokinesis
• Cytoplasm divides and two separate
daughter cells are produced
Mitosis
• Each cell now has 46
chromosomes (same it
started with)
• Each new cell grows until
it is ready to divide
Mitosis
• All body cells in
humans are made
through mitosis
• Sex cells (egg &
sperm) are NOT
made through mitosis
Put It All Together!!!
Animal Cell Mitosis
All Cells are Different!!
• All cells live for
different lengths of
time
• Cells carry out
mitosis at different
speeds to replace
cells that are worn out
Brain cells
30-50 yrs
Red Blood Cells
120 days
Platelets
10 days
Stomach Lining
2 days
Cells
Liver Cells
Intestine Lining
200 days
3 days
Cells
Skin cells
20 days
Mitosis
• In which body organs do cells carry out
mitosis the most often?
Stomach, Intestine, Skin
• In which body organs do cells carry out
mitosis the least often?
Brain
Plant vs. Animal Cell Mitosis
• Plant cells do not have
centrioles
• There is no furrowing in
telophase. A cell wall
forms instead.
Put It All Together!!!
Plant Cell Mitosis
Flaws in Mitosis
When cells are dividing out of control,
tumors are produced
Cancer is one type of tumor that can result
from out of control mitosis
Mutations
• Mutations = random mistakes in DNA
copied during Interphase
• Can result from UV radiation, genetics,
smoking, etc.