PART 3 Honors Genetics Ms. Day Mitosis and Cancer PART 3 Honors Genetics Ms. Day

Another Type of Cell Division: Binary Fission Prokaryotes (bacteria) Reproduce by a type of cell division called binary fission

The bacterial chromosome replicates In binary fission, The bacterial chromosome replicates The two daughter chromosomes move apart Origin of replication E. coli cell Bacterial Chromosome Cell wall Plasma Membrane Two copies of origin Origin Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. 1 Replication continues. One copy of the origin is now at each end of the cell. 2 Replication finishes. The plasma membrane grows inward, and new cell wall is deposited. 3 Figure 12.11 Two daughter cells result. 4

The cell cycle is HIGHLY regulated The frequency of cell division Varies with the type of cell These cell cycle differences Result from regulation at the molecular level http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html

Cell Cycle Checkpoints The clock has specific checkpoints a critical control point stop and “go-ahead” signals  regulate cycle signals report whether crucial cellular processes up to that specific point have been completed and completed correctly There are 3 checkpoints G1 checkpoint G2 Checkpoint M checkpoint

The Cell Cycle Control System Figure 12.14 Control system G2 checkpoint M checkpoint G1 checkpoint G1 S G2 M

G1 Checkpoint G1 checkpoint G1 G0 If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in cell cycle. If a cell does not receive a go-ahead signal at the G1checkpoint, cell exits the cell cycle and goes into G0, a nondividing state. Figure 12.15 A, B

G1 Checkpoint Right before S phase Checks cell size & original DNA for damage Makes key decisions  will cell divide or enter G0 (resting) phase Some cells enter a resting state (G0) permanently

G2 Checkpoint Checks cell size Checks for DNA damage/mutations (from replication) Occurs at END of G2  starts M phase

M Checkpoint Makes sure spindle is correctly attached to EACH chromosome Makes sure all chromosomes are aligned correctly at the mitotic plate In a single file line!

Chromosomes are lined up in middle of cell

The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases Two types of regulatory proteins in cytoplasm are involved in cell cycle control Cyclins Cyclin-dependent kinases (Cdks)

CYCLIN DEPENDENT KINASE (CDK) INACTIVE FORM CYCLIN DEPENDENT KINASE (CDK) CYCLIN + ACTIVE FORM CDK/CYCLIN COMPLEX

Active vs. Inactive?? What happens when cyclins and cdks are in the ACTIVE form? Cells can pass through the cell cycle to the NEXT phase    What happens when cyclins and cdks are in the INACTIVE form? Cells can NOT pass through the cell cycle to the NEXT phase 

cyclin degrades & breaks apart cyclin degrades & breaks apart “OFF”  RED LIGHT cyclin degrades & breaks apart

What degrades (breaks down) cyclins? Proteolytic enzymes (proteins) Break down/degrade cyclins  cause them to fluctuate in [ ] “PROTEO” means protein “LYTIC” means break or lyse REMEMBER: Cyclin concentration fluctuates (changes) Cdk concentration stays the SAME

Different Cyclins and CDKs for each checkpoint Cyclin D-CDK4 Cyclin E-CDK2 Cyclin A-CDK2 Cyclin B-CDC2

Control of Cell Cycle Animations http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html Amination #8 http://www.cellsalive.com/apop.htm

Programmed Cell Death (Apoptosis) http://www.dnatube.com/video/1188/Apoptosis-animation If cell does NOT pass checkpoints it might need to be killed! Cell signaling is involved in programmed cell death needed to maintain healthy tissues/ cell function 2 µm Figure 21.17

What CONTROLS the Checkpoints? Both internal (inside the cell) and external (outside the cell) signals

Internal and External Signals Internal signals DNA replication Growth/Nutrition CDK/Cyclins External signals Growth factors & Hormones Density Dependent Inhibition Anchorage Dependence

External Influences on Cell Division Growth factors & hormones Stimulate other cells to divide Density-dependent inhibition Crowded cells stop dividing Most animal cells exhibit anchorage dependence Cells must be attached to a structure to divide Ex: extracellular matrix of a tissue other protein or cells

Normal mammalian cells. Cells anchor to dish surface and divide (anchorage dependence). When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition). Normal mammalian cells. **The availability of nutrients, growth factors, and a substratum for attachment limits cell density to a single layer. (a) 25 µm Figure 12.18 A

Cancer cells Exhibit neither density-dependent inhibition nor anchorage dependence Immortal cells (if enough nutrients) 25 µm Cancer cells usually continue to divide well beyond a single layer, forming a clump of overlapping cells. Figure 12.18 B

Loss of Cell Cycle Controls in Cancer Cells Do not “listen” to control mechanisms (internal and/or external) CONTINUE TO DIVIDE Form tumors TUMOR= mass or group of abnormal dividing cells

Why are Cancer cells IMMORTAL? Don’t need growth factors  maybe they make their own growth factors Mutations in GENES!!! Ex: cyclin or Cdk genes CANCER IS CAUSED BY A LOT OF MUTATIONS (AN ACCUMULATION OF MUTATIONS)

Loss of Cell Cycle Controls in Cancer Cells Normal cell  cancer cells using process of transformation Form tumors Benign  “fine” Clump of cells remain at orginal spot Malignant  “mean” “cancer” Loose/destroy attachments to other cells  they can spread!!!

Malignant tumors These tumors invade surrounding tissues and can metastasize Tumors that can SPREAD and form secondary tumors USE BLOOD STREAM and LYMPH VESSELS TO SPREAD!!!

Pre-cancerous group of cells = polyp Tumor Glandular tissue Cancer cell Blood vessel Lymph vessel Metastatic Tumor Cancer cells invade neighboring tissue. 2 Cancer cells spread through lymph and blood vessels to other parts of the body. 3 A tumor grows from a single cancer cell. 1 A small percentage of cancer cells may survive and establish a new tumor in another part of the body. 4 Figure 12.19

Cancer Treatment Radiation Chemotherapeutic drugs destroys DNA in cancer cells (so can’t divide) Chemotherapeutic drugs interfere with specific steps in cell cycle (Ex: spindle formation or function) also effects normal cells  Ex: hair loss

Cancer Causing Agents Genetics (inherited) Spontaneous mutation Envinromental Mutagens (a.k.a- carcinogen) Sun Viruses Chemicals

Cancer Animations- REVIEW Cancer Movie https://www.youtube.com/watch?v=46Xh7OFkkCE Called Cancer Quest http://science.education.nih.gov/supplements/nih1/cancer/activities/activity2_animations.htm

Flashcard Vocabulary http://highered.mcgraw-hill.com/sites/0078757150/student_view0/vocabulary_eflashcards.html