Download Cell Cycle teacher notes Pre-AP 14-15

Cell Cycle Notes --PreAP
I. DNA – Deoxyribonucleic acid; located in nucleus
A. Long and thread-like DNA in a non-dividing cell – chromatin
B. Thick, short, coiled doubled DNA in a dividing cell – chromosome
1. chromosome consists of 2 parts:
a. chromatid
b. centromere – protein tab holds 2
sister chromatids together
2. chromosomes are divided into segments called – genes
C. Illustration: chromatin to chromosomes
duplicates
itself
chromatin
coils up into
chromosome
II. Cell Cycle – the repeating sequence of growth and division of a eukaryotic cell
A. The cell spends most of its time in – Interphase
1. cell grows, DNA is loosely wound, and cell carries out normal functions
2. 3 phases:
a. cell grows and matures – G1 (first growth)
G1 phase
b. chromatin duplicates – S (synthesis)
c. organelles replicate and
cell prepares for division – G2 (second growth)
S phase
G2 phase
B. Division of the nucleus – mitosis
C. Division of the cytoplasm and organelles – cytokinesis
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
cell plate
III. Mitosis – division of the nucleus into 2 nuclei, each with the same number and kind of chromosomes
A. HANDOUT
B. 4 phases PMAT
1. chromosomes condense, nuclear envelope breaks down, spindle fibers form – Prophase
2. chromosomes line up along equator – Metaphase
3. chromatids separate, centromere divides, and move to opposite poles – Anaphase
4. chromosomes uncoil, new nuclear envelope forms, spindle fibers break down – Telophase
C. Mitosis occurs only in body cells, or – somatic cells
D. 2 new cells formed have same number and kind of chromosomes as original
1. original cell called – parent cell
2. cells formed are known as – daughter cells
Parent Cell
2
Daughter
Cells
E. Many organisms, especially unicellular organisms, reproduce by means of cell division--called asexual reproduction ex: bacteria
F. Chromosome Number
1. number of chromosomes each organism has in its cells varies from species to species
example: human = 46
lettuce = 18
dog = 78
gorilla, chimp = 48
2. all cells (except the sex cells) in an organism have the same number of chromosomes
example: human = 46
skin cells = 46
muscle cells = 46
cardiac (heart) cells = 46
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 – proteins called cyclins
a. cyclins initiate the various stages of cell cycle
2. cell cycle checkpoints -- regulate progress of cell cycle
a. ensure that damaged DNA not passed on to daughter cells
b. G1 checkpoint at end of G1 phase -- determines whether cell is ready to divide or not
c. G2 checkpoint at end of G2 phase – check to make sure DNA replication is complete
d. M checkpoint at Metaphase–check for whether chromosomes properly attached to spindle fibers
3. injuries affect rate of cell division
a. cells at edge of injury stimulated to divide rapidly -- producing new cells
b. when healing is completed, rate of cell division -- slows down and returns to normal
4. when cells come into contact with each other in culture, they stop dividing
H. Uncontrolled Cell Growth
1. control over cell cycle can break down resulting in -- cancer
2. cancer cells do not respond normally to – signals that regulate cell division
3. cells divide uncontrollably forming -- tumors and can invade other tissues
4. mutations in DNA leading to tumors can be caused by:
a. chemicals – smoking or asbestos (lung cancer)
b. radiation – sun -- UV rays (skin cancer)
c. viruses – HPV (cervical cancer) or hepatitis (liver cancer)
d. immune system disorders – HIV (many different cancers)
e. heredity – genetics
5. p53 – “ guardian of the genome”
a. plays role in triggering control mechanisms at checkpoints -- suppresses tumors to prevent cancer
b. p53 can either – repair faulty DNA
or – kill off cell if it can’t be repaired (apoptosis)
c. problems with gene p53 -- related to more than 50% of all cancers
Cell Cycle – Mitosis (p.246-247 text)
Prophase
duplicated chromosomes
nuclear envelope
breaking apart
spindle
fibers
form
Interphase
centrioles
Metaphase
nuclear
envelope
(middle)
chromatin
spindle fibers
centriole
Anaphase
(away)
Individual
chromosomes
Telophase
(two)
nuclear envelope
reforming
chromosomes
unwind into
chromatin
Cytokinesis
Complete for review:
Phase
Chromosome Appearance
and/or Location
Important Events
Interphase
DNA/chromatin copies
itself
DNA Replication
Cell grows and replicates
organelles
Prophase
Chromosomes coil up
Nuclear envelope disappears
Spindle fibers form
Metaphase
Chromosomes lineup in the
middle
Spindle fibers connect to
chromosomes
Anaphase
Chromosome copies divide
and move apart
Spindle fibers pull
chromosome copies apart to
opposite poles
Telophase
Chromosomes uncoil back
into chromatin
Nuclear envelopes reform
2 new nuclei are formed
Spindle fibers disappear
Cytokinesis
Chromatin
Division of the rest of cell’s
cytoplasm and organelles