Disease Storyline
Cell cycle and mitosis 
Body cells divide for growth of an organism or repair of damaged tissue. This creates two genetically identical to the original cell.
Interphase = G1, S, G2
Mitosis “nuclear division” = Prophase, Metaphase, Anaphase, Telophase
Cytokinesis “cytoplasmic division”
Cancer cell division is our of control division of mutated cells compared to normal cell division
Checkpoint proteins not doing their job
Apoptosis not occurring
Contact inhibition not happening
Normal cells
Controlled growth (function properly)
Stop growing when in contact with other cells
Appearance: even cell shape/size, one nucleus, normal chromosome number
Can induce apoptosis (cell death) when damaged
Cancer cells
Rapid uncontrolled growth (excessive growth)
Mutated signal tells the cells to divide when they shouldn’t
Do not stop growing when in contact with other cells
Appearance: uneven cell shape/size, 1-3 nuclei, abnormal chromosome number
CANNOT induce apoptosis when damaged
Due to mutations in the DNA (tumor suppressor genes or DNA repair genes)
Many cancer cells lose their proper function
Leukemia
Cancer cells that end up pile up on one another form tumors - No contact inhibition.
Malignant cancer cells can migrate to other regions of the body
Cancer cells divide in less time than normal cells (448 minutes vs. 625 minutes)
Cancer cells do not differentiate. This means they do not become specialized cells (specialized cells could be red blood cells, bone cells, skin cells, etc.)\
Cancer cells do not maintain homeostasis (i.e. a balance of the appropriate amount of cells needed in a location)
The process of healing
When you cut your skin, a signal is sent out for clotting factors to be released to stop the bleeding.
These factors protect the area beneath the cut to allow for new cells to grow (or divide).
As new cells grow they will come in contact with nearby cells, which allows for the cells to stop dividing.
In tumors (or cancer cells), contact inhibition does not function. Cancer cells keep growing and eventually pile up on each other.
Proto-oncogenes - regulatory proteins that stimulate the cell cycle
When the time is right (size of cell is appropriate and no DNA damage is present) these proteins will tell the cell to continue through the cell cycle
Tumor suppressor genes: regulatory proteins that halt (stop) the cell cycle
When the cell is too small or there is damaged DNA these proteins will stop the cell cycle in attempt to fix the problem.
If the errors cannot be corrected the cell will be programmed to go through apoptosis (cell death)
DNA = DeoxyriboNucleic Acid
DNA has a double helix shape aka spiral staircase = this means that two strands twist around each other
DNA is made up of repeated NUCLEOTIDES
Each nucleotide contains:
1 phosphate group
1 deoxyribose sugar
1 of the 4 nitrogenous bases (A, T, G, C)
Backbones are antiparallel - facing opposite directions, and allows for the hydrogen bonds to form between the bases
DNA replication: the process of making a copy of DNA
Purpose: To have TWO complete sets of DNA for cellular division
Parent Strand (template strand or original strand)
Daughter Strand - complementary bases will be laid down to match the parent strand
P53
P53 is activated when a cell is stress, low in oxygen, has DNA damage, or is exposed to chemotherapy.
→ p53 activates (or TURNS ON) other genes for expression - this mean that p53 causes other proteins to be made
These proteins can be repair proteins (to fix DNA damage) or proteins that induce apoptosis (cell death)
IF MUTATED, p53 cannot cause the creation of proteins to fix DNA or induce apoptosis
Meiosis is a special type of cell division in sexually reproducing organisms that produces gametes (the sex cells, or egg and sperm).
It involves two rounds of division that reduces the number of chromosomes in half, resulting in four genetically different cells having only one copy of each chromosome.
Human sex cell begins a diploid - 2n = 46 chromosomes and splits off to two n=23 cells in meiosis 1 and then four n=23 in meiosis 2
Mitosis vs Meiosis
Same: Produces new cells, similar basic steps, starts with a single cell parent cell
Different Mitosis: Creates all body cells, produces 2 diploid daughter cells which are genetically identical. There are 4 stages in total, and genetic variation does not change. Purpose is for healing and growth and is asexual production. Include prophase, metaphase, anaphase, and telophase. No crossing over
Different Meiosis: There are 8 stages in total, which produces 4 haploid daughter cells with 23 chromosomes each. Genetic variation is increased as well. Purpose is for sex cells and sexual production. Divides twice with one set of chromosomes. Each daughter cell is genetically unique and has the same phases as mitosis but doubled. Crossing over occurs in prophase