You are performing mitosis. Where is this occurring? Describe what is happening.
-
Upload
morgan-willis -
Category
Documents
-
view
217 -
download
0
Transcript of You are performing mitosis. Where is this occurring? Describe what is happening.
![Page 1: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/1.jpg)
You are performing mitosis.Where is this occurring?
• Describe what is happening.
![Page 2: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/2.jpg)
One billion cells/gram
• The human body consists of a huge number of cells, on the average about one billion cells per gram of tissue.
• Each cell nucleus contains our entire hereditary material (DNA), located in 46 chromosomes (23 pairs of chromosomes).
![Page 3: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/3.jpg)
Mitosis
• Nuclear division plus cytokinesis– Produces two identical daughter cells –Part of cell cycle
![Page 4: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/4.jpg)
Cell Cycle
• Set of events in cell growth and division• Some cells cease to divide and are not
considered to be part of the cell cycle.– Examples are: Cells from the heart, eye, and N.S.
• Cell cycle duration – 8 minutes in some embryos– as long as one year in liver– Most mammalian cells about 24 hours.
![Page 5: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/5.jpg)
Cell CycleTaken fromhttp://www.biologycorner.com/resources/cell_cycle.jpg
![Page 6: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/6.jpg)
Stages of Cell Cycle
• G1 – Gap 1
• S – Synthesis – when DNA is replicated• G2 – Gap 2
• M – Mitosis – when chromosomes separate and cytokinesis occurs
![Page 7: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/7.jpg)
G1
• Cells grow in size– Produces RNA and synthesize protein
• Cells may become quiescence - no longer proliferating– Cells maintain themselves
• An important cell cycle control mechanism activates (G1 Checkpoint) – It ensures that everything is ready for DNA
synthesis.
![Page 8: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/8.jpg)
S phase – DNA synthesis
• Cell replicates genetic material • A family of enzymes make an exact replica of
the DNA. • In human cells, just 6-hours are needed to
replicate 46 chromosomes– totalling six billion nucleotides, kept in exact
sequence as parental DNA– A mistake = mutation
![Page 9: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/9.jpg)
G2 Phase
• Cell continues to grow and produce new proteins.
• At the end of this gap is a control checkpoint (G2 Checkpoint) to determine if the cell can enter M (mitosis) and divide.
![Page 10: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/10.jpg)
M Phase - Mitosis
• Cell growth and protein production • All of the cell's energy is focused on the
complex and orderly division into two similar daughter cells.
• Mitosis lasts one to two hours. • There is a Checkpoint in the middle of mitosis
(Metaphase Checkpoint) that ensures the cell is ready to complete cell division.
![Page 11: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/11.jpg)
Regulation/Control of the cell cycle
• How cell division (and thus tissue growth) is controlled is very complex.– Errors can lead to uncontrolled cell growth –
which is how tumors are formed
• The passage of a cell through the cell cycle is controlled by proteins in the cytoplasm.
![Page 12: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/12.jpg)
Control of cell cyclehttp://www.campbell.edu/faculty/garrett/PHAR%20408/cell%20cycle%20checkpoints.jpg
![Page 13: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/13.jpg)
Primary G1/S cell cycle checkpoint
![Page 14: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/14.jpg)
Cyclins
–Levels rise and fall with the stages of cell cycle. –G1 cyclin (cyclin D)–S-phase cyclins (cyclins E and A)–mitotic cyclins (cyclins B and A)
![Page 15: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/15.jpg)
Cyclin
dependent kinase
• Cdks– G1 Cdk (Cdk4)– S-phase Cdk (Cdk2)– M-phase Cdk (Cdk1) Their levels in the cell remain fairly stable, but each
must bind the appropriate cyclin (whose levels fluctuate) in order to be activated.
They add phosphate to proteinThey are the major control switches for the cell
cycle, causing the cell to move from G1 to S or G2 to M.
![Page 16: You are performing mitosis. Where is this occurring? Describe what is happening.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f495503460f94c6ac93/html5/thumbnails/16.jpg)
Maturation Promoting Factor MPF
Triggers progression through the cell cycle• p53 – Protein blocks the cell cycle if the DNA is damaged– If the damage is severe this protein can cause
apoptosis (cell death).
• p27– a protein that binds to cyclin and cdk blocking
entry into S phase.