Download Chapter 20 - Roslyn Public Schools

Topic 08
Mitosis
I. Mitotic Cell Division
A. Mitosis – used for growth, repair, and asexual
reproduction - the chromosomes in the nucleus are
duplicated - the cell divides along with the cytoplasm
to form two identical cells - occurs in stages – the
cells produced are identical to each other and the
original cell they came from
–
1. Interphase - time between cell divisions - the
chromosomes are replicated (duplicated) - the
two identical strands are attached at the
centromere and the individual strands are known
as chromatids
a. A closer look at interphase – most of
the time is spent in interphase

(1)3 stages – G1, S, and G2
– (a.)G1 – intense biochemical and biosynthetic
activity and growth – the cell doubles in size and
new organelles such as mitochondria, ribosomes,
and centrioles are produced.
– (b.) S – synthesis of DNA takes place – each
chromosome is replicated
– (c.) G2 – cell prepares for mitosis by making any of
the components that the cell needs to complete cell
division
–
2. Prophase - spindle fibers become visible - nuclear
membrane disintegrates – first actual step of mitosis – the
chromatin shortens and thickens to become chromosomes
–
3. Metaphase - the double stranded
chromosomes become attached at the spindle
fibers and move to the center of the cell (equator)
– second step of mitosis

4. Anaphase - centromeres replicate and
then separate - spindle fibers shorten and
pull the chromatids apart – 3rd step
–
5. Telophase - nuclear membrane forms around
each new set of chromosomes - the new nuclei
have the same number and types of
chromosomes as the original nucleus – last step

B. cytoplasmic division – also known as
cytokinesis - at the end of mitosis, the
cytoplasm divides and you have two new
daughter cells - if this does not occur, you
end up with one cell that has two nuclei
Stages of mitosis
Stages of Mitosis

C. differences between mitotic cell division in
plant and animal cells
–
–
1. Animal cells contain centrioles which aid in cell
division
2. In plant cells, a cell plate is formed that
becomes the new cell wall. In animal cells, the
cell pinches in to form two separate cells
Mitosis Animation
http://vcell.ndsu.nodak.edu/animat
ions/

D. uncontrolled cell division - invades
surrounding tissue and interferes with their
normal functions - known as cancer
II. Asexual Reproduction
A. definition - does not include two parents or
the fusion of two nuclei - has one parent that
reproduces by mitosis

B. methods of asexual reproduction
–
1. Binary fission - cytoplasm and nuclear material
divide equally to form two daughter cells that are
equal in size
–
2. Budding - a new organism grows off the side of the
parent - may either separate or live as a colony - the
daughter cell is smaller than the parent cell
–
3. Sporulation - spores are released by the parent
- when conditions in the environment are
favorable, they will produce new organisms
–
4. Regeneration - when lost parts grow into new
organisms - ex. Starfish and planaria
–
5. Vegetative propagation

a. bulbs - enlarged, underground stems - surrounded by
leaves - grows into a new plant – example: various flowers

b. tubers - enlarged, underground stem with buds grows into a new plant – example: potato

c. runners - horizontal stems that grow along the ground
- these stems enter the ground and grow into new plants
– example: strawberries

d. cuttings - a piece of a plant is put in water and grows
roots which can be planted

e. grafting - put two plants together
III. Biotechnology

A. Cloning - producing identical offspring
from a single cell of an organism – take DNA
from one organism and transfer it to an
zygote – see board
Click and Clone

B. Genetic engineering - transfer of genes
from one organism to another producing
recombinant DNA – see example on board

C. Human Genome – mapped out human
DNA