Lecture 8b Flashcards
Prophase in mitosis
nuclear envelope still intact (nuclear membrane present), replicated chromosomes condense
Mitotic spindle just being assembled
chromosomes condense
Chromatin = DNA + Protein
Chromosome= Condensed chromatin
But
We’ll use the terms chromosomes & condensed chromosomes
Chromosome = DNA + Protein
Centrioles: anchor for spindle fibers
Prometaphase
nuclear envelope breaks down.
Mitotic spindle complete & attaching to all the condensed replicated chromosomes
Metaphase
Replicated condensed chromosomes are aligned at the metaphase plate by the spindle fibers
Anaphase
Early anaphase: sister chromatids separated by mitotic spindle fibers: sister chromatids each now called an unreplicated chromosome
Later anaphase: unreplicated condensed chromosomes being moved towards the centrioles (at the poles of the cell) by spindle fibers.
Telophase
Early telophase:
Chromosomes almost at the poles of the cell
No nuclear membrane yet
Cleavage furrow present
Late telophase:
Nuclear membrane reforms, unreplicated chromosomes decondense
Once nuclear membrane complete: MITOSIS COMPLETE
Cytokinesis
Division of cytoplasm to form 2 daughter cells
Usually begins during telophase
But not part of mitosis
Ring of protein filaments encircles the cell & contracts, forming a cleavage furrow → splits cell into 2 daughter cells
Mitosis vs cytokinesis
When mitosis is complete: 2 daughter nuclei (in 1 parent cell)
Late cytokinesis
1 parent cell with 2 nuclei
When cytokinesis is complete: 2 daughter cells are formed
Plant Cells mitosis and cytokinesis vs animal cells
Mitosis in plant cells is similar to animal cells, but no centrioles present
Cytokinesis: is different
Golgi forms a line of vesicles that fuse to become
the plasma membrane of each daughter cell AND
the cell plate: separates the daughter cells
Cell cycle in bacteria (prokaryotes)
Reproduce by binary fission, not mitosis
Asexual reproduction: replicate DNA then splint into 2 identical daughter cells
Mitosis – asexual, because no DNA from two different cells. One cell duplicated.
Cytokinesis: cleavage furrow & aseptum (new dividing wall), forms down the middle of the cell.
The septum itself splits down the middle, and the two cells are released to continue their lives as individual bacteria.
Binary fission
Step 1- Replication of DNA. The bacterium uncoils and replicates its chromosome, essentially doubling its content.
Step 2- Growth of a Cell. …
Step 3-Segregation of DNA. …
Step 4- Splitting of Cells.
Checkpoint
A checkpoint in the cell cycle is a critical control point where stop and go-ahead signals regulate the cycle.
Check points regulate the cell cycle in eukaryotes
to be enforced…
Gene mutations can lead to …
Gene mutations can lead to loss of cell cycle regulation
Mutations can be inherited, but most are caused by the environment
Loss of cell cycle regulation can lead to tumor formation
Tumor: mass of cells. Benign vs cancerous.
All cancer due to a loss of cell cycle regulation
Cancer: when a tumor invades surrounding tissue or metastasizes
What can mutate genes
X-rays, certain viruses, bad diet, smoking, errors made during DNA replication,…
If specific genes get mutated and are not repaired - cancer
