Cell Cycle & Chromosome anatomy

12-Pro '24'25. Made by Nathan G.

Interphase

Nondividing phase & longest phase in cell cycle
Cell grows
a. DNA replicates
b. Nutrients accumulate
- Nuclear envelope still visible

Gap/Growth 1 (G1)

Rapid growth & attains normal size

Organelle duplication starts

Longest phase within interphase
- Muscle & nerve cells stay at this phase for whole life

Synthesis (S)

DNA replicated in the nucleus

Chromosomes double, gain 2 sister chromatids

Centrosome duplicated

Gap/Growth 2

Restores energy, grows, & creates proteins for mitosis

Organelle duplication ends

Mitosis/M-phase

Cell division done by somatic/body cells for:

Asexual reproduction
Growth & development
Tissue renewal

Prophase (Prepare)

Chromatin condense into chromosomes

Centrosomes move apart
Spindle fibers begin to form between centrosomes

-Chromatin microscopically visible

Metaphase (middle)

Chromosomes align on Metaphase plate

Nuclear envelope dissapears

Spindle fibers attach to kinetochores

Anaphase (away)

Spindle fibers each pull a sister chromatid apart

Telophase (together)

Nuclear membrane forms around each pole

Chromosomes decondense into chromatin

Spindle fibers breakdown

Post-mitosis

1. Cytokinesis

2. Both cells enter interphase

Cells are genetically equal w/ same ploidy

Cell cycle checkpoints

1. G1 - checks cell readiness for S phase

2. G2 - checks cell readiness for M phase

3. Spindle checkpoint (M) - checks spindle fiber attachment before anaphase

Meiosis

Cell division for sexual reproduction

Uses sex/haploid cells

Meiosis 1

Reductional

Halves chromosome count to haploids

Meiosis 2

Equational

Equivalent to mitosis

Prophase 1 (Meiosis)

Chromatin condenses into chromosomes

a. Pairs homologous chromosomes (Synapsis)
b. Does crossing over of genetic material at telomeres

Metaphase 1 (Meiosis)

Homologous chromosomes align on metaphase plate

Anaphase 1 (Meiosis)

Homologous chromosomes pulled away via spindle fibers

Nucleoli appear

Telophase 1 (Meiosis)

Separated chromosomes enclosed in different nuclei

Cytokinesis occurs after

Daughter cells become haploid

Prophase 2 (Meiosis)

Daughter cells’ chromosomes condense, spindle fibers form

Move towards metaphase plate

Metaphase 2 (Meiosis)

Daughter cells’ chromosomes align with each other, connect to spindle fibers

Anaphase 2 (Meiosis)

Daughter Cells’ chromosomes separate into sister chromatids

Telophase 2 (Meiosis)

Daughter cells have separated into 2, 4 total haploid cells

Fully separate via Cytokinesis after

Protein Kinase

Phosphorylation: Pass down phosphate group causing cellular response

CDK

Cyclin-dependent Kinase

Activity rises & falls w/concentration of cyclin in cell

Activates other kinases

e.g. MPF starts Mitosis

Centrosome

2 perpendicular centrioles

Produce spindle fibers

Centromere

Chromosome region joining sister chromatids

Made of cohesin

Kinetochore

Attachment point for spindle fibers on centromere

Spindle Fibers

Microtubule attaching to kinetochore to pull sister chromatids away

Chromatid

Duplicated chromosome DNA

Only classified as such when joined by cohesin

Density-dependent inhibition

Cells stop growing if one layer has been produced on container surface

Anchorage dependence

Cells must attach to something to divide