WEEK 5 Flashcards
(30 cards)
Detail the importance of the cell cycle
- allows for reproduction, growth, development and tissue renewal (replacement of cells)
- DNA must be replicated & evenly distributed between the two new cells
- Daughter cells also need other cell components, organelles, cytosol & plasma memebrane
Life cycle’s two periods
- Interphase - not dividing (comprises of three phases: G1, S, G2)
- Mitotic Phase - dividing (comprising of mitosis (M) & cytokinesis (C) )
What is interphase?
Period between cell divisions. Cell grows, develops and prepared for division
Define mitosis?
Process of nuclear division (karyokinesis), which is followed by cytoplasmic division (cytokinesis)
G1 chromatin VS Mitotic chromosomes
- Interphase cells (G1 chromatin): Nuclear envelope present; Individual chromosomes can NOT be distinguished
- Mitotic cells (Mitotic chromosomes): Nuclear envelope is absent; Individual replicated chromosomes are highly condensed
What are the three stages of Interphase?
- G1- first gap phase
- S - synthesis phase
- G2 second gap phase
G1 phase
- cell grows
- undertakes normal metabolism
- prepares for S phase
- OPTIONAL: cell exists cell division (G0 phase)
G0 phase
- During G1, cells may exit the cell cycle in response to regulatory signals & enter non-dividing state where the cell ,maintains a constant size
- Cells may stay in G0 for an extended period, or indefinitely
- Cells may re-enter G1 phase
- Not all phase enter G0
S Phase
- DNA replicated (amount doubles)
- Centrosome completes replication
- Nucleus becomes enlarged
G2 Phase
- Further growth of cell and protein synthesis
- Centrosome maturation
- Cell prepares to divide
M phase (Mitosis)
- chromosomes condense
- nuclear envelope disintegrates
- chromosomes attach to Mitotic spindle & move cell midpoint
- sister chromatids pulled to opposite poles of cell Karyokinesis (nuclear division, partitioning of DNA progeny cells)
- nuclear envelope reforms
- Cytokinesis (division of cytoplasm)
Mitosis Phases
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
Prophase
Chromosomes condense and Mitotic crinkle forms
Prometaphase
Nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores
Metaphase
Chromosomes align on the metaphase plate; spindle assembly checkpoint
Anaphase
Sister chromatids separate, becoming individual chromosomes that migrate towards spindle poles
Telophase
Chromosomes arrive at spindle poles, the nuclear envelope re-forms, and the condensed chromosomes relax
Cytokinesis
Cytoplasm divides; cell wall forms in plant cells
Mitosis VS Meiosis
Mitosis: 2 cells with the same number of chromosomes as the parent cell are produced … somatic cell division
Meiosis: cells with 1/2 the number of chromosomes as the parent cells are produced … gamete (sex cell) production
- ensures genetic material is not doubled in new generations of sexually reproducing organisms
Meiosis Phases
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
- Cytokinesis
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
- Cytokinesis
Prophase I
Chromosomes condense, homologous chromosomes synapse, crossing over takes place, the nuclear envelope breaks down, and the mitotic spindle forms
Metaphase I
Homologous pairs of chromosomes line up on the metaphase plate
Anaphase I
The two chromosomes (each with tow chromatids) of each homologous pair separate and mover toward opposite poles
Telophase I
Chromosomes arrive at the spindle poles
