Unit 6 Biology
Cell cycle
2 phases
Interphase
G0
G1
S
G2
Mitotic
Mitosis
Cytokinesis
Hayflick limit
How many times can a cell divide?
as the cells divide, the telomeres(or caps on the end of the chromosomes) eventually shorten over time until they disappear.
with each division, some of the actual chromosome information will be lost,
the cell cannot functionally divide properly
A cell can replicate itself around 50 times.
click to edit
CDKs
Enzymes
always inside of the cell
not functional until a cyclin attaches to it.
Cyclins
Proteins
expressed for a short time
accumulate within a cell
. Once they get to a certain concentration in the cell, the cyclins bond to the CDKs.
CDK-cyclin complex binds to a protein
gives it a phosphate group.
Cyclin is destroyed
Cdk’s lie dormant
This means that whenever cyclin levels rise, mitosis occurs cyclin levels fall back down, and the cycle repeats.
G0
Resting phase
The cell is neither dividing nor preparing to divide
Some cells stay in this phase for their entire lifespan
Neurons are permanently in the G0 phase and never divide.
S
G1
Make proteins and organelles for DNA synthesis.
Get Bigger
Most growth
A complete copy of DNA is created
In nucleus
DNA synthesis
G2
Rapid cell growth
Protein synthesis
Cell prepares for mitosis
click to edit
Type of cell division
2 Daughter cells created
Equal amount of chromosomes
4 phases
Prophase
The spindle fibers form
the DNA condenses into sister chromatids or chromosomes
The nuclear membrane surrounding the DNA disintegrates
Metaphase
the chromosomes line up in the middle of the cell
the spindle fibers attach to a sister chromatid each
Anaphase
the microtubules containing the spindle fibers are moved apart
Chromatids are pulled away from each other to opposite sides of the cell
Telophase
The spindle fibers disintegrate
The DNA unwinds back into normal DNA
The nuclear membrane reforms around the DNA.
click to edit
Physical process of cell division
After mitosis
Dividing the cytoplasm
Two daughter cells
Occurring at the same time as telophase
Cancer
Disease
The body’s cells grow uncontrollably in a certain area
Spreads to other parts of the body
Can occur in the Cell cycle due to mutations
Oncogenes
These are altered forms of genes known as proto-oncogenes.
responsible for promoting cell growth.
When altered or mutated, they become oncogenes and then can promote tumor formation or growth.
Usually Acquired
Having a mutation in just one of the two copies of a particular proto-oncogene is enough to cause a change in cell growth and tumor formation.
Tumor suppressor genes
3 main functions
Growth arrest
Growth arrest is where the cell stops growing due to mutation/damage, due to crowding, or lack of food.
DNA Repair
DNA Repair is when p53 finds a mutation and reports it to other proteins so that they can come and repair a mutation in the DNA.
Apoptosis
apoptosis is activated when p53 finds irreparable DNA damage, and there is no other way to maintain function other than to self-destruct.
DNA repair genes
Both slow down the cell cycle to repair or suppress mutations in the DNA.
Can be acquired or inherited
Characteristics of cancer affected cells
They stimulate their growth
They ignore growth-inhibiting signals
They avoid death by apoptosis
They develop a blood supply: angiogenesis
The tumor sends out signals saying “Feed me”
Nearby blood vessels extend and attach to the tumor to supply it
provides a passageway for tumor cells to move
They leave their site of origin to invade other tissues: metastasis
They replicate continuously to expand their numbers
They evade or outrun the immune response
click to edit
Types of DNA
3 forms
Chromatin
DNA tightly condensed into coils
Makes up Chromosomes
condensed into chromosomes during the prophase of mitosis.
Chromosomes
Made of chromatids
Either one or two
Made of one before replication
Made of two after replication
During telophase of mitosis, the chromosomes unwind back into regular DNA.
Sister Chromatids.
V like structure
The pair is held together by a centromere