Download CELL REPRODUCTION

Pre-Discussion Thinking Questions:
•To be considered LIVING or ALIVE, organisms must
be able to REPRODUCE. What does this mean?
•Why is it important for an organism to be able to
reproduce?
• What must happen in order
for reproduction to occur?
• You need…
DNA
• Genetic material found in the nucleus of all
cells. DNA is your genetic blueprint
(instructions) for all your cell’s activities and
all the characteristics of an organism.
DNA
• DNA stands for
DEOXYRIBONUCLEIC
ACID
• DNA has specific
segments, called
GENES. Each gene
controls one
particular trait,
although sometimes
more than one gene
can control one trait.
DNA
• DNA is shaped like a
twisted ladder (also
called a double helix).
It has sides (like the
handrails of a ladder)
and rungs (called
bases). The bases
are what provide a
code. The code tells
your cells and whole
body what to do.
Chromosomes
• Made of long strands
of DNA
• You have 46
chromosomes in your
cells (23 PAIRS.) One
SET came from
“MOM” and one from
“DAD”. The pairs are
held together by a
CENTROMERE.
Chromosomes
• Play an
important part
in cell division;
• Also called
CHROMATIN
CELL
REPRODUCTION
• At this very moment, cells all over
your body are growing and
dividing. How does this happen?
• Just as organisms go through
stages, or a life cycle, so do CELLS.
• Most of a cell’s life is spent in a period of
growth & development called INTERPHASE
• During this time, the cell is NOT dividing.
Cells that no longer
DIVIDE are always in
interphase.
Examples include
NERVE CELLS, BRAIN
CELLS.
• Cells that actively divide—such as SKIN cells—
have a more complex cell cycle.
• The process through which cells
divide is called MITOSIS
MITOSIS
(My-toe-sis)
• Also known as regular cell division.
• Two cells are created from one
• Each new cell has a nucleus that
contains the same number and type of
CHROMOSOMES as the original cell
MITOSIS (My-toe-sis)
Important to Remember!
• Human cells have 46
chromosomes in their nuclei,
so after cell division, each new
nucleus will have 46
chromosomes—not 23, because
the chromosomes duplicate
themselves before the cell
divides.
• (So at one point during cell division,
your cells actually have 92
chromosomes!)
Plant Cell Mitosis
—same process with a few twists!
• Because plant cells have rigid WALL, they
do not PINCH IN like animal cells do.
• Instead, they form a structure called a CELL
PLATE , where a new CELL WALL will form
ASEXUAL REPRODUCTION
• Reproduction by one parent organism
• Offspring that are produced by asexual
reproduction have DNA that is
IDENTICAL to that of its one parent.
ASEXUAL REPRODUCTION
• Regular cell division
is considered asexual
reproduction.
• Some organisms use
asexual
reproduction to
create whole new
organisms from just
one parent.
Types of Asexual Reproduction
Budding
• Budding is a type of asexual
reproduction where the new organism
GROWS FROM THE BODY of the
parent and when it becomes large
enough, it BREAKS OFF & lives BY
ITSELF.
• Examples include: YEAST, HYDRA,
AND SPIDER PLANTS,
Budding
Hydra
Strawberries
Spider plants
Potatoes
Types of Asexual Reproduction
Regeneration
• During regeneration, a whole organism may
develop from just a PART of the organism.
• Or you can get 2 ORGANISMS when there is
injury to ONE.
• Examples include: SEA STARS, SEA SPONGES,
PLANARIA
Regeneration
Types of Asexual Reproduction
Fission
• This process divides
them into two EQUAL
PARTS. (just like
splitting something
in half evenly)
• Bacteria are organisms
that divide by fission
Asexual Reproduction Clip
Cloning
• Cloning is asexual
reproduction, because
there is only one parent
providing DNA for the new
organism, which would
make the offspring
genetically identical to its
one parent.
• Not a new process—people
have been performing it for
thousands of years on
plants!
Cloning
• Scientists have cloned a
few animals, like Dolly
the sheep in 1997
Cancer
• When cells don’t STOP dividing the way
they are supposed to
• Results in the growth of a tumor (mass of
cells)
• Some tumors are benign (harmless) and
some are considered dangerous (when
they don’t stop growing, they can spread
to other parts of the body)
Cancer
How is this different from asexual
reproduction???
Sexual Reproduction
• New organism is produced when sex
cells from two different parents join
together.
• Offspring that are produced by sexual
reproduction have DNA that is
DIFFERENT compared to both of its
parents.
Sexual Reproduction
• Most plants and animals
reproduce in this manner.
• Remember what we call the
reproductive part of a plant?
Flowers!
• Males make one kind
of sex cell, called the
sperm.
• These are produced
by the testes.
SPERM
EGG
• Females make one kind of sex cell,
called the egg.
• These are produced by the ovaries.
• Sex cells are usually different in size.
• Sperm are small,
with all of the
genetic material
crammed into the
“head”.
• Eggs are large.
• Why might this be
so?
• Once two sex cells
have joined, we say
that fertilization
has occurred.
• The new cell that
forms is called a
zygote.
• If you have an egg
cell with 10
chromosomes
joining a sperm cell
with 10
chromosomes, how
many chromosomes
will the new baby
cell (the zygote
have)?
• 20
• A human body cell
has 23 pairs of
chromosomes
• A human sex cell
has only 23
individual
chromosomes.