Transcript CELL DIVISION

CELL DIVISION
• BIG IDEA: organisms
grow, reproduce, &
maintain themselves
through cell division.
• Cell division occurs in all
organisms
• Cell division is part of the
cell cycle.
• Both sexual & asexsual
reproduction involve cell
division
CELL DIVISION OCCURS IN
ALL ORGANISMS
• CELL DIVISION IS INVOLVED IN MANY
FUNCTIONS
– Occurs in all organisms; unicellular organisms
reproduce through this; in multicellular, cell division
allows for growth, development, repair and aids in
reproduction.
• GENETIC MATERIAL OF EUKARYOTIC
CELLS IS ORGANIZED IN CHROMOSOMES
– When a cell divides, each new (daughter) cell gets a
full set of genetic material (DNA).
• CELL DIVISION IS INVOLVED IN GROWTH,
DEVELOPMENT & REPAIR
Genetic Material of Eukaryotes
Organized into Chromosomes
• When a cell divides, each
new cell needs a complete
set of genetic material
• This is DNA
(deoxyribonucleic acid);
contains data for cell’s
growth & functions.
• Made of 2 strands of
material twisted together
into a double helix
(shown by Watson &
Crick)
• Most of DNA is in
nucleus as a mass of loose
strands called chromatin
• Before a cell divides,
DNA gets copied, then
starts to tightly wrap
around proteins to make
CHROMOSOMES (2
identical chromatids held
together by centromere)
• All human body cells
have 46 chromosomes,
fruit flies have 8 and corn
plants have 20.
CELL DIVISION USED TO
GROW, DEVELOP & REPAIR
• We all started as 1
cell26 billion when
born100 trillion as
adult
• In multicellular
organisms, cell division is
needed for growth,
development, and repair.
• As an organism grows &
increases its number of
cells, many become
specialized to do specific
jobs.
• When an organism is
injured or aged, its
worn out cells get
replaced by new
healthy cells via cell
division. (your throat
cells only last about
2-3 days).
Growth & Development
• Larger organisms just have
more cells (not larger). Cell
size is limited by its surface
area to volume ratio. (When it
gets too big, it divides into 2
smaller cells to function betterstill not sure why).
• During development, cells
become specialized to do
certain jobs.
• These cells may take on shapes
or structures to help them do
their jobs (long, thin nerve
cells or layered skin cells).
They still have the same DNA
as other cells in the body.
REPAIR
• Body repairs injuries by cell division.
• When skin is cut, skin cells on either side of cut
make new cells to heal the wound.
• As cells age & die, they need to be replaced. Human
body is made of about 200 different types of cellswhich are replaced at different rates. Skin cells wear
out quickly, so replaced quickly (about 40,000 every
minute). Brain cells live a long time (many years)
and don’t divide very often.