Mitosis, Meosis & Cell Cycle Flashcards
Mitosis
- Creates 2 identical diploid (2n) somatic daughter cells with 46 chromosomes
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
Prophase
- Nuclear Envelope breaks / Nuclear membrane dissolves
- Chromatin condenses
- Centriole pair in Centrosomes separates
- Formation of Mitotic Spindle
**Duplicated DNA (92 chromosomes)
Metaphase
- Chromosomes lines up at the metaphase plate under guidance of spindle fibers
- Mitotic Spindles pull on Kinetichores on the Centromere
Anaphase
- Cell elongates because Centromeres are pushed outward
- Microtubules from Mitotic Spindles shorten
- Sister Chromatids separate
Telophase
- Reverse of Prophase
- Nuclear Envelope and Nuclear Membrane reforms
- Chromosomes decondense into Chromatin (unravel)
- Mitotic Spindle breaks
- Nucleoli reappear
Cytokinesis in Mitosis
Cell begins to pinch in (as Telophase begins to occur)
- Cell divides (cytoplasm and organelles) creating two identical daughter cells
*Diploid (2n) cells are created with 46 chromosomes each
Chromatin
DNA wrapped around histones
Chromosome
Condense DNA (during cell division) made from chromatin
Kinetichore Proteins
On Centromere; pinches the center where spindle fibers will attach
G1 Phase
PreSynthetic Gap:
- Cell is metabolically active
- Growth
- Duplicate organelles and cytosolic components for energy and protein production
- Begin replicating centrosomes
G1 / S Checkpoint
Restrictions Stage:
Did everything grow and duplicate properly? DNA is examined and repaired
S Phase
“Synthesis” - DNA is replicated
S / G2 Checkpoint
Is DNA ok? Correct? Is there enough organelles and cytoplasm to divide between the two daughter cells?
G2 Phase
PostSynthetic Gap:
- Growth
- Enzymes and proteins are synthesized
- Centrosomes are replicated
M Phase
Mitotic Phase and Cytokinesis - nucleus divides; cytoplasm and organelles are divided into two daughter cells
G0 Phase
- Exit from the cell cycle (non-dividing)
- Cell goes about it job in the body and just exist
**Nerve cells stop here and remain here
Interphase
Duplication of DNA and organelles
G1 phase, S phase and G2 phase
Cell Cycle
G1 Phase G1 / S Checkpoint S Phase S / G2 Checkpoint G2 Phase M Phase Cytokinesis (G0 Phase) - Exit
Meiosis I
Reproductive Division:
- Occurs in Gametes or Sex Cells
- Creates two copies of everything in the cell during Interphase to create Double Diploid (2n) cells with 92 chromosomes
- First round of division to create 2 Double Haploid (n) cells: 23 chromosomes from mother and 23 chromosomes from father in each cell = 46 chromosomes total
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
- Cytokinesis
Prophase I
- Nuclear Envelope breaks
- Centrosomes separate
- Spindle fibers form
- Chromatin Condenses into chromosomes
**Crossing over occurs here
Chromatid
Single (1 parent) strand
Sister Chromatids
Double haploid (1 parent) but two copies of the strand
Cohesin
Holds sister chromatids together
Metaphase I
- Homologs line up at metaphase plate
- Spindle Fibers attach to kinetichores on cetromere (what holds the homologous pairs together)
- Separate homologous pairs
Anaphase I
- Disjunction: Homologous chromosomes pulled apart (breaking kinetichores) and pushed to opposite poles of the cell
- Sister chromatids still attached together by cohesin
- Cell elongates
Telophase I
- Nuclear envelope reforms around sister chromatids
Cytokinesis in Meosis I
- Cell begins to pinch in (as Telophase I begins)
- Cell divides creating 2 double haploid (n) daughter cells (23 chromosomes from mother and 23 chromosomes from father in each cell)
Meoisis II
Equational Division:
- No DNA replication between meiosis I and meiosis II; Centrosomes will replicate
- Begins with double haploid (n) cells with 46 chromosomes
- Results in 4 haploid (n) gamete cells with 23 chromosomes each
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
- Cytokinesis
Prophase II
- Nuclear envelope breaks
- Nucleoli disappear
- Centrosomes separate
- Centrioles migrate to opposite poles
- Spindle Fibers form
- Chromatin condenses
Metaphase II
- Sister chromatids line up at metaphase plate (turned by 90 degrees)
- Spindle fibers attach to kinetichores on centromere
Anaphase II
- Cohesin breaks
- Sister chromatids are pulled apart
- Cell elongates
- Centromeres divide and move to opposite poles
Telophase II
- Nuclear Envelope and Nuclear Membrane reforms
- Chromatids decondense into chromatin
Cytokinesis
- Cell begins to pinch in (at the start of telophase)
- Cell divides into 4 hapoid (n) gamete cells with 23 chromosomes each
Mitosis Review
- Somatic Cells
- Asexual
- Require 1 parent
- Identical daughter cells (no genetic advantage)
- Fast
- Produce 2 Diploid (2n) daughter cells with 46 chromosomes each
Meiosis Review
- Germ (sex) cells ; Gametes
- Sexual
- Require 2 parents
- Brand new cells / organism is created (genetic variation)
- Slow
- Produce 4 Haploid (n) daughter cells with 23 chromosomes each
Tetrad and Homologs
Code for the same things but are from two different parents (found in meosis)
Spermatogenesis
Primary Spermatocyte (2n) Undergoes Meiosis 1 Secondary spermatocyte (n) Undergoes Meiosis II Spermatids (n) - haploid Mature into 4 Haploid (n) Spermatozoa
**RESULT: 4 Sperm Cells
Oogenesis
Primary Oocyte (2n) Undergoes Meiosis I Secondary Oocyte (n) + Polar Body Undergoes Meiosis II Ootid (n) - haploid + Polar Body Mature into the Haploid Ova + 2-3 Polar Bodies (which will die)
RESULT: 1 Ova
Synapsis
Prophase I: Homologous chromosomes come together and intertwine with each other
Chiasma
Prophase I: Point of synapsis where recombination and crossing over may occur
Interkinesis
Telophase I and Cytokinesis: Partial uncoiling of the chromosomes
Centrosome
Contain the centrioles
Aster
Anchors the centrioles to the membrane
Disjunction
Anaphase I: Homologous chromosomes pulled apart (breaking kinetichores) and pushed to opposite poles of the cell
Control of Cell Cycle
Cyclins and Cyclin Dependent Kinases complex which phosphorylate transcription factors to promote transcription of genes required for the next stage of the cycle
