Page 250 amp 251 50 000 of the cells in your body will be replaced with new cells all while you read this sentence Review of cell cycle In multicellular organisms cells divide for ID: 499528
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Slide1
Regulating the Cell Cycle
Page 250 & 251 Slide2
50 000 of the cells in your body will be replaced with new cells, all while you read this sentence.Slide3
Review of cell cycle
In
multicellular
organisms,
cells divide for
growth, development, and repair of the organism
.
Slide4
The Cell CycleSlide5
The Cell Cycle
There are three main parts to the cell cycle:
interphase
mitosis
cytokinesis
Slide6
There are three phases to
interphase
:
G
1
- Growth and normal metabolic processes
S - Synthesis (DNA replication)
G
2
- Growth and preparation for mitosis
Slide7Slide8
But not all
somatic cells
undergo mitosis and those that do, do so at different rates (see page 249 in your text).Slide9
Cell growth and division are tightly controlled in eukaryotic multicellular organisms. Slide10
Cells in a petri
dish
Cells placed in a nutrient-rich broth in a petri dish will grow and divide until they meet each other or the sides of the dish. (page 250)
If some cells are removed, those cells remaining in the petri dish will grow and divide until the dish is full again.
Think of your body as a petri dish. Slide11
Cell cycle regulators discovered
Early 1980s
Group of biologists
Discovered that cells in mitosis contain a protein that, when injected into a non-dividing cell, caused mitotic spindles to form (remember spindles attach to the chromosomes)
Discovered that the amount of this protein in the cell depended on the phase of the cell cycle the cell was inSlide12
Cyclins
They called this protein
cyclin
because it seemed to regulate the cell cycle.
We now know that there are many closely related proteins involved in regulating the cell cycle in eukaryotic cells. As a group, they are called
cyclins
.
Slide13
There are 2 types of
cyclins
:
- internal regulators
- external regulatorsSlide14
Internal regulators are:
Proteins that respond to events inside the cell.
They allow the cell to proceed to the next phase of cell division only when the phase before it has been successfully completed.
Ex. All chromosomes must be replicated before cell enters prophase; all chromosomes are attached to spindles before entering anaphase.Slide15
External regulators are:
Proteins that respond to events outside the cell.
They direct the cell to speed up or slow down the cell cycle.
Molecules on the surface of the outside of cells signal cells around them to slow down or to stop cell growth (growth regulators).
Ex. Healing of wounds; embryonic developmentSlide16
Uncontrolled cell growth
Page 252
The consequences of uncontrolled cell growth in a
multicellular
organism are severe.
Cancer cells are cells that are not producing the proper
cyclins
or that do not respond to signals from the
cyclins
.Slide17
Cancer cells divide uncontrollably and form masses of cells called
malignant
tumours
that damage surrounding tissues.
Some of the cells may break off a malignant
tumour
, enter the blood stream or lymphatic system and travel to other areas of the body where they begin to grow.Slide18
Tumours
in which cells do not travel to other parts of the body or
neighbouring
cells are called
benign
tumours
,
and are not cancerous.
Tumours
whose cells do travel to other parts of the body or
neighbouring
cells are called
malignant.
The process by which cells from a malignant
tumour
travel to other parts of the body is called
metastasis.Slide19
Metastatic
cancer has the same name and
is the
same type of cancer
as
the original, or
primary
cancer. For example, breast cancer that spreads to the lung and forms a metastatic tumor is metastatic breast cancer, not lung cancer.Slide20
Gene p53
Some studies have shown a link between some cancers and a defect in a protein called p53.
In
humans, p53 is encoded by the TP53 gene located on the short arm of chromosome 17Slide21Slide22
Chromosome 17Slide23
In its anti-cancer role, p53 works through several mechanisms:
It can activate
DNA repair proteins
when DNA has sustained damage.
It can arrest growth by holding the
cell cycle at
the G
1
/S regulation point on DNA damage recognition (if it holds the cell here for long enough, the DNA repair proteins will have time to fix the damage and the cell will be allowed to continue the cell cycle).
It can initiate
apoptosis,
the programmed cell death
, if DNA damage proves to be irreparable.Slide24
How Cancer Develops
https://www.youtube.com/watch?v=46Xh7OFkkCESlide25Slide26
Cancer and the Immune System
Killer T-cells
http://www.youtube.com/watch?v=HNP1EAYLhOs
Slide27
You should know…
What chemicals regulate the cell cycle? How do they work?
What happens when cells do not respond to the signals that normally regulate their growth?
How do cells respond to contact with other cells?
Why can cancer be considered a disease of the cell cycle?
How do cancer cells differ from noncancerous cells? How are they similar?
What is a malignant
tumour
? A benign
tumour
;
metastasis.