Mitosis and Meiosis

Interphase

• 90% of the cell cycle

• 3 Phases:

  • G1 Phase: the cell grows by producing proteins and organelles

  • S phase: DNA synthesis or replication occurs

    • Beginning: each chromosome is a haploid

    • End: after DNA replication each chromosome consists of two sister chromatids

  • G2 Phase: The cell grows more and prepares for cell division

• Mitosis

  • 10% of the cell cycle

  • → cytokinesis

G2 of Interphase

• It consists of chromosomes which were duplicated in S phase which are condensed and cannot be individually seen

• A nuclear envelope encloses the nucleus which contains all of the chromosomes

• Centromeres: are formed

Prophase

• Chromosomes are condensed and can be individually seen

• Each duplicated chromosome appears as two identical sister chromatids join at the centromeres

• Centromeres: move away from each other attached together by miotic spindle

Prometaphase:

• The chromosomes are even more condensed

• Kinetochore: a special protein that forms at the centromeres of each chromatid (two per chromosome)

Metaphase “Meet”

• Chromosomes: are lined at the middle

• Kinetochores: for each chromosome of the sister chromatids are attached to the micotubles

• Centromeres: at opposite ends

Anaphase “Apart”

• Chromosomes: the two sister chromatids of each pair separate and become a distinct chromosome. Each one is pulled to one side of the cell by the microtubules attached to the centromeres

Telophase

• Two daughter nuclei form in the cell

• Chromosomes become less condensed

• Spindles: gone

• The cell is like two blobs which split into

Cytokenesis

Prophase → Metaphase (two sister chromatids = one chromosome) Anaphase ( one chromatid = one chromosome?)

Chromosomes: contain genetic material