Chapter 4 Section 1 Cell Division and Mitosis
A. Cell division- increases the number of cells and causes many-celled organisms to
grow.
B. The Cell cycle- series of events that takes place from one cell division to the next.
a. Cells have periods of formation, growth, and developments, and death
called lifecycles.
b. Interphase- most of the life of any eukaryotic cell, or cell with a nucleus is
spent in a period of growth and development
i. During interphase, a cell duplicates it chromosomes and prepares
for cell division
ii. After interphase, the nucleus divides and then the cytoplasm
separates to form two new cells.
C. Mitosis- process in which the nucleus divides to form two identical nuclei.
a. Chromosome- a structure in the nucleus that contains hereditary material.
b. Prophase
i. Nucleolus and Nuclear membrane disintegrate
ii. Centrioles move to opposite sides of the cell
iii. Spindle Fibers begin to stretch across the cell
c. Metaphase- pairs of chromatids line up across the center of the cell.
d. Anaphase
i. Each centromere divides
ii. Each pair of chromatids separates and moves to opposite ends of
the cell.
e. Telophase- spindle fibers disappear and a new nucleus forms
D. Division of the Cytoplasm- for most cells, the cytoplasm separates after the
nucleus divides
a. In animal cells the cell membrane pinches in the middle and the
cytoplasm divides.
b. In plant cells, a cell plate forms
E. Results of mitosis
a. Each cell in your body, except sex cells, has a nucleus with 46
chromosomes, 23 pairs.
b. Allows growth and replaces worn out or damaged cells
F. Asexual reproduction – a new organism is produced from one parent organism
a. An organism with no nucleus divides into two identical organisms by
fission.
b. Budding- a small exact copy of the adult grows from the body of the
parent
c. In regeneration a whole new organism grown from each parent piece.