Cell Cycle Flashcards
What are somatic cells?
Somatic cells are all other cells except germ cells or reproductive cells.
Eg. Nerve cells, skin cells, blood cells
The cell cycle
Is the series of events that cells go through as they grow and divide
What happens during the cell cycle?
During the Cell Cycle, a cell grows, prepares for division and divides to form two daughter cells, each of which begins the cycle again.
What are the 3 stages of the Cell Cycle?
Interphase (G1, S, G2)
Mitosis (PMAT)
Cytokinesis
How long does the process take in mammalian cells?
24 hours
How long does the process take in bacteria?
approx 20 minutes
Interphase
is the period of growth that occurs between cell division. It’s main purpose is to replicate the DNA located in the cell.
What is the connection point in chromosomes called?
Centromere
What happens during G1 (Interphase)?
This is where the cell will do most of its growing. The cell will increase in size and synthesize new proteins and organelles.
What happens during S (Interphase)?
The DNA within the cell is replicated to ensure that the new cell will end up with the correct amount of DNA. It also replicates chromosomes and synthesis DNA.
What happens during G2 (Interphase)?
The cell continues to get ready and produces proteins required for spindle fibre formation. By the end of this stage, the cell is approx double its original size.
What are the stages in mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens in mitosis stage?
Chromosomes can be viewed due to them thickening and condensing in size.
What are duplicate chromosomes known as?
Sister Chromatids
What happens in Prophase?
The nuclear membranes break down and spindle fibers are formed. Chromosomes become condensed and visible.
What happens in Metaphase?
The double stranded chromosomes line up along the equator of the cell.
What happens in Anaphase?
Sister chromatids are separated and pulled to opposite ends of the cells via spindle fibres.
What happens in Telophase?
The nuclear membrane is reformed and chromosomes decondense.
What happens in Cytokinesis?
Two nuclei are formed. Redistribution of organelles take place around the new nuclei. It physically separates.
What is the cell cycle for Prokaryotes called?
It’s known as binary fission
Shape of DNA in Eukaryotes
Twisted double helix structure
Shape of DNA in Prokaryotes
Circular shape
Purpose of checkpoints:
To ensure that the replicated cells are not damaged and will continue to work as well as the original
What does the p27 do?
p27(cell cycle brakes)-is a protein that halts the cell cycle at G1.
What does the checkpoint at G1 check?
A check of the DNA of the cell will take place. If the DNA is found damaged or incomplete, the cell is stopped from continuing.
G0
Is the non-dividing quiescent stage.
What is the p53?
It’s the ‘security guard’ at G1 checkpoint.The p53 gene is a tumour-suppressor gene that checks for damage to DNA during interphase of the cell cycle.
What does the checkpoint at G2 check?
(p21)- the replicated DNA of the cell is checked for completeness and lack of damage.
What does the checkpoint at M (or spindle assembly checkpoint) check?
It occurs at the Metaphase stage of mitosis. A check is carried to ensure that the sister chromatids are attached to the correct microtubules of the spindle. It also checks that the sister chromatids are pulled in opposite directions to diff. poles of the spindle.
Why do we need a cell cycle?
Growth, Repair and Maintenance (production of new cells to replace damaged or dead cells) and Reproduction
Cell Cycle in Mammals
There are range of cells that are constantly actively dividing
Eg. Skin(epidermis), Gut (epithelial lining) and Bone Marrow
When are skin cells replaced?
Every 48 days, the entire epidermis layer is replaced.
Where do skin cell originate from?
Basal Stem cells
When are Gut cells replaced?
4-5 days
Where do gut cells arise from?
Intestinal stem cells
Cell cycle in other animals
Many other animals use the cell cycle for regeneration. Eg. Starfish (lost arms regenerate by mitosis)
Cell cycle in plants
Only non-permanent tissues/cells will go through the cell cycle
Where are Meristematic Tissues found?
Tips of roots and shoots
What are Meristematic Tissues responsible for?
Growth in plant girth and length
Cell cycle in Fungi
Growth via mitosis and usually from a single spore. Spores are also formed via mitosis
When the cell cycle goes wrong
Psoriasis
- Overproduction of the skin cells but decreased cell loss (buildup of cells)
- Affected checkpoints and regulatory mechanisms
When the cell cycle goes wrong
Cancer
- When the cell cycle becomes uncontrolled
- Production of masses/tumours
- Usually involves a mutation in the gene that codes for one of the checkpoint proteins
When the cell cycle goes wrong
Malignant Tumours
- Individual cells can break free of the original mass and travel through the body and establish a secondary site.
