BIOA01H3 Lecture Notes - Lecture 21: G2 Phase, G1 Phase, Dna ReplicationPremium

3 pages206 viewsFall 2018

Biological Sciences
Course Code
Aarthi Ashok, Shelley Brunt, Mark Fitzpatrick

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BIOA01 Lecture 18: Mitosis and Cell Division, Role of Microtubules and Microfilaments
- Cell Division: process where cells make more cells
o Is considered a highly controlled event meaning that cells have to regulate their
cell cycles
Any mistakes made during it will lead to negative effects to cell
o Process must satisfy 2 important requirements
1: parent cell must be large enough at the end of the process to divide
into 2 cells
2: Daughter cells must receive the full amount of genetic info from the
parent cell
o Cancer: uncontrolled cell division resulting from mutations in genes controlling
cell division
o Binary Fission: prokaryotic cell division
- Eukaryotic Cell Cycle
o 2 distinct phases
1: M phase (2 hours): Parent cell divides into 2 daughter cells
2: Interphase (10-18 hours): Time between two successive M phases
o Interphase: composed of 3 subsections
Gap phases: all about preparation
G1 Phase: cell increases size and protein content
o Cell prepares to undergo DNA replication
G2 Phase: cell prepares to enter mitosis and cytokinesis
S Phase: Phases of DNA replication
Entire DNA content in the nucleus is replicated
Sequence of interphase = G1 phase, S phase, G2 phase
G0 Phase: distinct from the G phases and S phase
Present in cells that do not actively divide
No active preparation for cell division
o Mitosis: takes place in 5 stages
From G2 phase to the start of mitosis, the chromosomes condense and
become more visible
1: Prophase: chromatin fibers and presence of microtubules cause DNA
to start condensing into X like shape
Chromatin condensation forms chromosomes
Centrosomes form MTOC: enables us to start to see microtubules
2: Prometaphase: microtubules start attaching to chromosomes
Chromosomes separated to opposite poles of cell
o Preparation for next phase: metaphase
o Microtubules attach to the kinetochore region on
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