Understanding the Cell Cycle: From Chromosomes to Cell Division, Slides of Biology

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Biology is the only subject in

which multiplication is the same

thing as division…

2007-2008 Docsity.com

The Cell Cycle:

Cell Growth, Cell Division

2007-2008 Docsity.com

And now look at you…

How did you

get from there

to here? Docsity.com

Getting from there to here…

• Function of cell division

• making new cells
• continuity of life
  • asexual reproduction
    • unicellular organisms
  • growth
  • repair & renew

• Cell cycle

• life of a cell from

origin to division into

2 new daughter cells

amoeba

nuclear pores nuclear pore

nuclear envelope

nucleolus

histone protein

chromosome

Nucleus^ DNA

• Function

– protects DNA

• Structure

• nuclear envelope
  • double membrane
  • membrane fused in spots to create pores
    • allows large macromolecules to pass through

What kind of molecules need to pass through?

 actin  microtubule  nuclei

Cytoskeleton

Centrioles

• Cell division

• in animal cells, pair of centrioles

organize microtubules

• spindle fibers
• guide chromosomes in mitosis

Getting the right stuff

• What is passed on to daughter cells?

• exact copy of genetic material = DNA
  • mitosis
• division of organelles & cytoplasm
  • cytokinesis

chromosomes (stained orange) in kangaroo rat epithelial cell → notice cytoskeleton fibers Docsity.com

Overview of mitosis

interphase prophase (pro-metaphase)

metaphase anaphase telophase

cytokinesis

I.P.M.A.T.

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Cell cycle

• Cell has a “life cycle”

M Mitosis

G Gap 1

G Resting

G Gap 2

S Synthesis

cell is formed from a mitotic division

cell grows & matures to divide again

cell grows & matures to never divide again

G 1 , S, G 2 , M G 1 → G 0

epithelial cells, blood cells, stem cells

brain / nerve cells muscle cells

liver cells

Interphase

• Divided into 3 phases:
  • G 1 = 1st^ Gap
    • cell doing its “everyday job”
    • cell grows
  • S = DNA Synthesis
    • copies chromosomes
  • G 2 = 2nd^ Gap
    • prepares for division
    • cell grows (more)
    • produces organelles, proteins, membranes

G 0

Copying / Replicating DNA

• Synthesis phase of Interphase

• dividing cell replicates DNA
• must separate DNA copies correctly to 2

daughter cells

• human cell duplicates ~3 meters DNA
• each daughter cell gets complete identical copy
• error rate = ~1 per 100 million bases
  • 3 billion base pairs in mammalian genome
  • ~30 errors per cell cycle » mutations (to somatic cells)

Organizing DNA

• DNA is organized in

chromosomes

• double helix DNA molecule
• wrapped around histone

proteins

• like thread on spools
• DNA-protein complex =

chromatin

• organized into long thin fiber
• condensed further during

mitosis

DNA

histones

chromatin

duplicated mitotic chromosome

ACTGGTCAGGCAATGTC

double stranded chromosome