14.2 Cellular Reproduction Flashcards
Cdk Inhibitor Arrests Cell Cycle Progression
- p27 alters conformation of Cdk catalytic subunit
- Inhibits protein kinase activity
- p27 drapes itself over cdk2 inhibiting the activity
- age matched but not sized match because p27 has proliferated growth
- p27 knockout thymus gland huge compared to normal due to increased number of cells
Mitosis
- Process of nuclear division that faithfully partitions duplicated chromosomes
- Five stages-Prophase, Prometaphase, Metaphase, Anaphase, Telophase
Cytokinesis
Division of cell that partitions cytoplasm into two cellular packages
Prophase
- Chromosomal material condenses to form compact chromosomes.
- Cytoskeleton is disassembled and mitotic spindle is assembled.
- Golgi complex and ER fragment. Nuclear envelope disperses (partially due to disassembly of lamin protein).
Prometaphase
- chromo start associating with spindle fibres
- Chromosomal microtubules attach to kinetochores of chromosomes
- Chromosomes are moved to spindle equator.
- congressing to plate
Metaphase
•Chromosomes are aligned along metaphase plate, attached by chromosomal microtubules to both poles.
Anaphase
- Centromeres split, and chromatids separate.
- Chromosomes move to opposite spindle poles.
- Spindle poles move farther apart
Telophase
- Chromosomes cluster at opposite spindle poles.
- Chromosomes become dispersed.
- Nuclear envelope assembles around chromosome clusters.
- Golgi complex and ER reforms.
- Daughter cells formed by cytokinesis
Condensin and Cohesin
- Condensin-forms loop around DNA loops
- Cohesin-forms loop around sister chromatids
- Alternative Model: Cohesin forms molecular bridges between sister chromatids
- either way it keeps the sis chromo together
- these is just a way to condense and pack the chimes other than histones
Where along the chromo is it tightly or loosely packed?
- Held tight at centermeere and loose at end.
- Due to polo-like kinases and aurora b kinase which phophorylate the cohesion, and is inactive along length of chromo but not at centromere. •Phosphatase active counteracts the kinase at centromere.
- This is where they’re quickly phosphorylated and then quickly dephosphoralated.
- will only separate at anaphase
Roles Kinetochore Structure
- Roles
Site of attachment to mitotic spindle - Location for motor proteins
- Component of signaling pathway for cell cycle checkpoint
Kinetochore Structure
- kinetochore has microfillimous called fibrous corona.
- end associates with kinetocore.
- Dynene and kineasein moved in particular directions.
- Dynein – moves toward minus end of microtubule
- CENP-E (kinesin) – moves toward plus end of mt
- Depolymerase-specialized kinesin protein responsible for depolymerizing mt during anaphase
- NDC80 is a multisubunit protein that connects microtubule to kinetochore
Formation of Mitotic Spindle
- Spingle apparatus. Come from either side of the cell.
- 2 centrosomes make up a centriole MTOC
- If you look at G1 it’ll only have 1 centrosome. As enters S phase, its synthesis of additional centrosome, as enters into mitosis they migrate to opposite ends. Form spindle apparatus.
- Phosphorylation of centrosomal protein by Cdk2 initiates duplication
- these procentrioloes enlongate during G2
- Centrosomes migrate to opposite poles in mitosis
Abnormal Centrosome Number
In this case there’s 3 centrosomes. Chromo don’t know where the metaphase plate is. Abnrnal chromosome segregation can be related to abnormal centrosome segregation, additional duplication.
how to plants assemble a spindle fibre apparatus with the presents of a centrosome?’
•centrosomes are unique to animals, none in plants. Different mechanisum, uses 2 headed motor proetins. Jumble of cspindle fibres but there’s these motor proteins present. M.Tubules have plus and minus end. When the proteins grab them they \d then start moving towards the minus end and as they move they pull the m.Tubules togtheretr like a drawstring. Create the equivalent of a centrosome.Plant cells set up the spindle apparatus without the centrosome.
•SUMMARY:
Use 2 headed minus directed motor proteins and associated micro tubules that move towards the minus end and [ ] the minus ends together at the pole of the cell.
