THE CELL CYCLE

• As eukaryotic cells grow and divide, they move

through three distinct stages:

1. interphase – cells grow and prepare to divide

2. mitosis – cells start to divide

3. cytokinesis – two cells are formed from one

1. Interphase:

• the cell carries out all normal life activities

• the DNA is in very long, thin, and invisible strands

• DNA is copied at end of interphase to get ready for

division

• most of the cell’s life is spent in interphase

2.5

HowStuffWorks

Videos "Interphase

: The Resting Stage"

2. Mitosis

• the DNA doubles, to get ready to be divided

• there are 4 phases of mitosis

i) Prophase:

• DNA thickens

• 2 identical strands of DNA (copied during interphase) called chromosomes

• chromosome made of 2 identical sister chromatids

• each chromatid held together by a centromere

• nuclear membrane disappears

• YouTube - Mitosis: The Phases, Part 1 of 2, from Thinkwell Biology

PHASES OF CELL DIVISION 2.5

ii) Metaphase

• centrioles move to either side of the cell• chromosomes line up in the middle of the

cell

iii) Anaphase• centromere splits and sister chromatids

separate• now called ‘daughter’ chromosomes• spindle fibres from centrioles pull them to

opposite sides of the cell

iv) Telophase

• final stage of mitosis• daughter chromosomes stretch out and get thinner• nuclear membrane starts to form around each gp of

daughter chromosomes• cell appears to have 2 nuclei (nucleus)

Cytokinesis

• cell’s cytoplasm divides• cell membrane pinches off• splits into 2 new daughter cells• each cell is identical to the original parent cell

YouTube - Mitosis: The Phases, Part 2 of 2 from Thinkwell Biology