What is cancer?
Uncontrolled cell growth.
How are cancerous cells different than normal cells?
They lack differentiation and they have no specialization.
They have the ability to continuously divide...
They have abnormal nuclei (w/ mutant nuclei)... apoptosis (programmed cell death) does not occur.
They form tumors because they continuously divide—they have no regulation of growth.
They metastasize - that is, they move away from their initial place.
What are tumors that invade surrounding tissues called?
Malignant—they have the ability to break away from the initial tumor mass and move away to other parts of the body.
How do tumor cells move?
The lymphatic system.
The circulatory system.
What is a cell cycle?
It represents all the phases the cell undergoes.
What is the longest phase of the cell cycle?
It is the interphase...
Most of the cell cycle is spent in this phase—most cell functions occur in this phase... It's basically 90% of the cell cycle.
Describe the three stages of interphase...
G1 - Cell doubles its organelles, synthesizes different proteins that regulate normal cell function, and accumulates materials to be used for making DNA.
S Stage - DNA making and replicating occurs here
The chromosome content DOUBLES - they are all replicated.
G2 - Cell makes proteins that assist in cell division.
What is mitosis?
It is the division of the nucleus... Chromosomes pairs are separated and one group moves to one pole of the cell and the other moves to the other pole of the cell.
What is cytokinesis?
It is the division of the cytoplasm that results in the splitting apart of the mother cell into two daughter cells. During this, duplicated chromosomes and cytoplasm are distributed equally to the two daughter cells.
*Each daughter cell receives approximately the same amount of organelles.*
When normal cell division occurs it is a highly regulated process... Why?
There are "checkpoints" along the way... At each "checkpoint" cell division STOPS. Proteins then survey the cell to make sure that it can continue on in the cell cycle. These checkpoints have to be passed in order for the cell to continue...
What happens if a problem is detected?
There can be two outcomes... Problem is fixed and cell continues or ... the cell kills itself (apoptosis).
When do "checkpoints" occur?
They occur during G1, G2 and the middle of M (mitosis)...
What are the genes that form the proteins that control the cell cycle called?
What happens when a proto-oncogene goes rogue (mutates)?
What happens when a proto-oncogene goes rogue (mutates)?
What are tumor suppressor genes?
They are a "back up" in case cell division goes wrong. They essentially make proteins that suppress the uncontrolled cell division. These genes, like proto-oncogenes can ALSO mutant and form proteins that mess up.
What is a common tumor suppressor that has mutated (causes cancer)?
P53 - over half of all cancer is caused by P53.
Recall - what two elements does mitosis involve?
Nuclear division and cytoplasmic division.
Inside the nuclei how many chromosomes are there?
What is a chromosome made of?
DNA - DNA is made of nucleic acid and nucleotides.
What do nucleotides contain?
Nucleotides contain one of four nitrogenous bases: Adenine, Guanine, Cytosine and Thymine.
What is DNA arranged into?
Genes - genes code proteins that determine our internal physiology and morphology (what we look like).
What determines the types of proteins produced?
The ORDER of the nitrogenous bases.
How many pairs of chromosomes do humans have?
23 - Total of 46 chromosomes.
Where do these 23 pairs come from?
One comes from mommy and one comes from daddy... All 46 chromosomes are the same shape and size...
TRUE or FALSE - the total DNA (total number of chromosomes) is copied during the S phase?
TRUE or FALSE - before the S phase each chromosome is a double strand of DNA?
FALSE - it is a single strand of DNA because it hasn't been copied yet.
How many sex chromosomes do we have?
When each DNA molecule is copied each strand has a duplicate strand - what are these strands called?
Where do these sister chromatids join together at?
The "centromere"; it's a narrow region on each strand.
TRUE or FALSE - when these two strands are joined together they are from then on referred to as single strands?
Before S phase how many chromatids do we have?
After S phase how many chromatids do we have?
Does the number of chromosomes change?
No, because each chromosomes after S phase is composed of two chromatids.
What happens during the "M" phase?
1 Mother Cell splits into two Daughter cells.
**during mitosis the number of chromosomes NEVER changes, though...
That means that the TWO daughter cells will have the same number of chromosomes as the mother cell.
What happens after the DNA is doubled in Mitosis?
The division of DNA occurs in the Prophase, Metaphase and Anaphase...
Describe the Prophase?
Protein filaments called "microtubules" migrate to the poles of the cell and join to organelles called centrioles.
The centrioles and microtubules are collectively called ... ? Centrosomes.
Describe the Metaphase?
The centrosomes have migrated to opposite poles of the cell.
The chromosomes move to the center of the cell and form basically a straight line.
They line up at an imaginary line called a metaphase plate.
Describe the Anaphase?
The microtubules contract and pull the sister chromatids apart.
At the end of all the "phases" how many chromatids are at each side of the poll?
46 on each side.
What happens in cytoplasmic division?
We have the telophase... Once the DNA has been divided in nuclear division the cell will split in two... Microtubules break down because their role is done...
Special filimanets then form a "contractile" ring around the cell separating the two poles.
Filaments begin to pinch and break the cell in two.
What happens to the daughter cells after all this has occurred?
They will go through their own cell cycle ... G1, S, G2, and M...