Download CELL DIVISION

Cell Cycle Notes -- PreAP
I. DNA –
A. Long and thread-like DNA in a non-dividing cell –
B. Thick, short, coiled doubled DNA in a dividing cell –
1. chromosome consists of 2 parts:
a.
b.
2. chromosomes are divided into segments called –
C. Illustration: chromatin to chromosomes
II. Cell Cycle – the repeating sequence of growth and division of a eukaryotic cell
A. The cell spends most of its time in –
1. cell grows, DNA is loosely wound, and cell carries out normal functions
2. 3 phases:
a. cell grows and matures –
G1 phase
b. chromatin duplicates –
c. organelles replicate and
cell prepares for division –
S phase
G2 phase
B. Division of the nucleus –
C. Division of the cytoplasm and organelles –
Occurs quickly
1. In animal cells the cytoplasm
pinches in
2. In plant cells a cell plate forms
D. After mitosis and cytokinesis, the cell returns to
Interphase
III. Mitosis – division of the nucleus into 2 nuclei, each with the same number and kind of chromosomes
A. HANDOUT
B. 4 phases
1. chromosomes condense, nuclear envelope breaks down, spindle fibers form –
2. chromosomes line up along equator –
3. chromatids separate, centromere divides, and move to opposite poles –
4. chromosomes uncoil, new nuclear envelope forms, spindle fibers break down –
C. Mitosis occurs only in body cells, or –
D. 2 new cells formed have same number and kind of chromosomes as original
1. original cell called –
2. cells formed are known as –
Parent Cell
E. Many organisms, especially unicellular organisms, reproduce by means of cell division--called
F. Chromosome Number
1. number of chromosomes each organism has in its cells varies from species to species
example:
2. all cells (except the sex cells) in an organism have the same number of chromosomes
example:
G. Regulating the Cell Cycle – not all cells move through cell cycle at the same rate
1. in eukaryotic cells, timing of the cell cycle is regulated by –
a. cyclins initiate the various stages of cell cycle
2. cell cycle checkpoints -a. ensure that damaged DNA not passed on to daughter cells
b. G1 checkpoint at end of G1 phase -c. G2 checkpoint at end of G2 phase –
d. M checkpoint at Metaphase -3. injuries affect rate of cell division
a. cells at edge of injury stimulated to divide rapidly -b. when healing is completed, rate of cell division –
4. when cells come into contact with each other in, culture they stop dividing
2
Daughter
Cells
H. Uncontrolled Cell Growth
1. control over cell cycle can break down resulting in -2. cancer cells do not respond normally to –
3. cells divide uncontrollably forming -4. mutations in DNA leading to tumors can be caused by:
a. chemicals –
b. radiation –
c. viruses –
d. immune system disorders –
e. heredity –
5. p53 – “ guardian of the genome”
a. plays role in triggering control mechanisms at checkpoints -b. p53 can either –
or –
c. problems with gene p53 --
Cell Cycle – Mitosis (p.246-247 text)
Complete for review:
Phase
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Chromosome Appearance
and/or Location
Important Events