C.12 - Mitosis Flashcards
Cell Division: Unicellular Organisms
Division of one cell reproduces the entire organism
Cell Division: Multicellular Organisms
Depends on cell division for growth, development, and repair
Cell Cycle
The life of a cell from formation to its own division
Genome
A cell’s endowment of DNA (its genetic information).
Can consist of a single DNA molecule (common in prokaryotic cells), or several DNA molecules (common in eukaryotic cells)
Chromatin
A complex of DNA and protein that condenses during cell division and forms chromosomes
Somatic Cells
Non-reproductive cells that have two sets of chromosomes (2 × 23 = 46 total)
Gametes
Reproductive cells: sperm and eggs. Have half as many chromosomes as somatic cells
Centromere
The narrow ‘waist’ of the duplicated chromosome; where the two sister chromatids are most closely attached though cohesion proteins
Cytokinesis
The division of the cytoplasm
Mitosis
The division of the genetic material in the nucleus
Meiosis
Produces Gametes; yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell
Cell Cycle Phases
- Mitotic (M) phase (mitosis and cytokinesis)
- Interphase (cell growth and copying of chromosomes in preparation for cell division; 90% of cycle)
Interphase Subphases
- G1 phase (‘first gap’)
- S phase (DNA ‘synthesis’; where chromosomes are duplicated)
- G2 phase (‘second gap’)
Five stages of Mitosis
Prophase•Prometaphase•Metaphase•Anaphase•Telophase
Interphase (G2)
Nucleus: Envelope is intact; Nucleolus is present
Chromosomes: Replicated; Not yet condensed Centrosome: Two centrosomes, each containing two centrioles (cylinder of microtubule triplets)
Prophase
- Nucleus: Nucleoli disappear; Envelope intact
- Chromosomes: Begin to condense; Sister chromatids visible
- Centrosomes: Begin moving to opposite poles; Begin forming mitotic spindle
Prometaphase
- Nucleus: Envelope degenerates
- Chromosomes: Highly condensed; Interacting with microtubules (mt); Kinetichore appears (proteins that attach centromeres to mts)
- Centrosomes: Extend mt to attach to chromosomes (kinetichore mt)–Extend mt to interact with other mt (non-kinetichore mt)
Metaphase
- Nucleus: No evidence
- Chromosomes: Line up on metaphase plate -Centrosomes: At opposite poles; Mt form ‘spindle apparatus’; Kinetichore mt (from each pole) interact with kinetichores (on sister chromatids); Non-kinetichore mt interact with mt from opposite pole
Anaphase
- Nucleus: No evidence
- Chromosomes: Sister chromatids pull apart (separate into two chromosomes); Centromeres lead the way
- Centrosomes: At opposite poles; Kinetichore mt shorten; Non-kinetichore mt lengthen
Telophase; Cytokinesis
- Nucleus: Two daughter nuclei begin to form; Envelope rebuilds; Nucleolus reforms
- Chromosomes: Decondense
- Centrosomes: One per daughter cell
- Cytoplasm: Formation of cleavage furrow pinches cell in two
Kinetochores
Protein complexes that form in association with the centromeres of chromosome
Cytokinesis: Plant vs. Animal
Animal: Forms Cleavage furrow
Plant: Cell plate forms
Binary Fission
How Prokaryotes reproduce.
Chromosome replicates and the two daughter chromosomes actively move apart. The plasma membrane pinches inward, dividing the cell into two
Cell cycle control system
Directs sequential events of the cell cycle.
Checkpoints where the cell cycle stops until a go-ahead signal is received–The G1, G2 and M
Signals are provided by two types of regulatory proteins interacting together–Cyclins–Cyclin-dependent kinases (Cdk)
