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33 Cancer
lecture powerpoint
29
Biology
Undergraduate 1
04/06/2011

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Term

 

density-dependent inhibition

is an example of what?

 

Definition

 

external signals...crowded cells stop dividing when this occurs. A reduction in cell division.

When a cell population reaches a certain density, the amount of required growth factors and nutrients available to each cell becomes insufficient to allow continued cell growth.

 

Term
What is anchorage dependence? 
Definition
most animal cells exhibit this. it means they must be attached to a solid surface in order to divide (for example the solid glass or plastic surface of a culture dish)
Term
What is apoptosis?
Definition
normal benign type of programmed cell death in which a cell shrinks, fragments its DNA, and alters its surface so as to activate the cell's phagocytosis by macrophages
Term
phagocytosis 
Definition
the process by which particulate material is engulfed ("eaten") by a cell. Prominent in predatory cells, such as Amoeba proteus and in cells of the vertebrate immune system such as macrophages 
Term
What happens when cells ignore apoptosis?
Definition

they continue to grow and divide despite external signals

cancer can occur

and failure in cell communication occurs

Term
Define cancer and what does it affect
Definition

"a group of diseases characterized by uncontrolled growth and spread of abnormal cells"

 

if affects cell cycle control

Term
What is the process by which a cell is converted to a cancerous cell?
Definition
transformation
Term
what are tumors?
Definition

masses of abnormal cells within otherwise normal tissue

Term
benign tumors
Definition
when abnormal cells remain at the original site
Term
malignant tumors
Definition
invade surrounding tissues and metastasize (export cancer cells to other parts of the body where they may form secondary tumors)
Term
Do cancer cells need growth factors to grow and divide?
Definition

not always.

-they may make their own growth factors

-they may convey a growth factor's signal without the presence of the growth factor

-they may have an abnormal cell cycle control system

Term
Cancer cells often have abnormal chromosomes. What is a gene translocation?
Definition

A translocation means that a piece of one chromosome has broken off and stuck on a different chromosome. Chromosome translocations cannot be repaired. If a translocation has not resulted in any genetic material being lost, it is known as a balanced translocation.

Term
The gene regulation systems that go wrong during cancer are the same systems that play important roles in_____ ______. They also regulate ____ ____ and ____.  
Definition

embryonic development

 

regulate cell growth and division

 

also codes for growth factors, their receptors and intracellular molecules of signalling pathways

Term
What are oncogenes?
Definition
cancer causing genes
Term
What are proto-oncogenes
Definition
normal cellular genes that code for proteins that stimulate normal cell growth and division
Term
tumor-suppressor genes
Definition
encode proteins that inhibit abnormal cell division
Term
What happens when a DNA change occurs making a proto-oncogene excessively active?
Definition
it converts it to an oncogene, which may promote excessive cell division and cancer
Term
Name the three different ways proto-oncogenes can be converted to oncogenes
Definition

- Point mutations (causing an increase in gene expression)

- Amplification - multiple copies of a section of a chromosome being reproduced

- Movement of DNA to a promoter (increasing transcription)

Term

When a proto-oncogene is converted to an oncogene what can result from the following

a. mutation in coding sequence

b. gene amplification

c. chromosome rearrangement 

Definition

a. hyperactive protein made in normal amounts

b. normal protein greatly overproduced

c. nearby regulatory DNA sequence causes normal protein to be overproduced, or fusion to actively transcribed gene produces hyperactive fusion protein

Term
What type of protein is the Ras protein?
Definition
a G protein
Term
What is the role of the Ras protein?
Definition
it relays a signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases
Term
What does the p53 gene do?
Definition

it encodes a tumor-suppressor protein

 

it is also a specific transcription factor 

 

it promotes the synthesis of cell cycle-inhibiting proteins for example when DNA is damaged

Term
what do mutations in p53 prevent?
Definition
suppression of the cell cycle
Term
Mutations that knock out the p53 gene can lead to what?
Definition
excessive cell growth and cancer
Term
Explain the development of colorectal cancer.
Definition
[image]
Term
Mutations in ras cause ....
Definition
production of hyperactive ras protein and increased cell division
Term
Incidence of cancer increases with age. Why?
Definition
multiple mutations are generally needed for full fledged cancer
Term

A cancerous cell is usually characterized by 

 

Definition

at least one active oncogene

the mutation of several tumor-suppressor genes

Term
Mutations in what genes are found in 50% of all breast cancers?
Definition
BRCA1 and 2
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