2.5.1 Outline the stages of the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis Interphase is the longest portion of a cell’s life and has three subdivisions: First Gap G1 http://commons.wikimedia.org/wiki/File:First_gap_cell_lifecycle.svg
Second Gap G2http://commons.wikimedia.org/wiki/File:Second_gap_cell_lifecycle.svg
Mitosis: 4 Main stages http://commons.wikimedia.org/wiki/File:Prophase_procariotic_mitosis.svgttp://commons.wikimedia.org/wiki/File:Metaphase_procariotic_mitosis.svgmedia.org/wiki/File:Anaphase_procariotic_mitosis.svghttp://commons.wiki The cell divides it’s chromosomes into 2 identical sets media.org/wiki/File:Telophase_procariotic_mitosis.svg Detail in 2.5.4
Stage EventsGap 1 (G1) • Protein Synthesis • Organelles produced • Cytoplasm increases in sizeSynthesis (S) DNA is duplicatedGap 2 (G2) • Organelles produced • Cytoplasm increases in sizeMitosis The cell divides it’s chromosomes into two identical sets 4 Stages • Prophase • Metaphase • Anaphase • TelophaseCytokinesis The parent cell divides into two daughter cells
2.5.2 State that tumours (cancers) are the result of uncontrolled cell division and that these canoccur in any organ or tissue. In cancerous cells, control of mitosis has been lost and they divide… and divide… and divide. This leads to tumours (cancer tissue) that displaces healthy tissue and interferes with proper function. Cancer can arise from any cells capable of mitosis Background: A Brenner tumour in an ovary. These are usually benign, but can be malignant http://commons.wikimedia.org/wiki/File:Brenner_tumour_intermed_mag.jpg
2.5.3 State that interphase is an active period in the life of the cell when many metabolicreactions occur, including protein synthesis, DNA replication, and an increase in the number ofmitochondria and chloroplasts. State: give a specific name, value or other brief answer without explanation or calculation The name ‘interphase’ implies a period of time between stages and that nothing much is going on. This is not the case! This is when the cell is going about it’s day-to-day ‘business’ i.e. carrying out it’s programmed functions and growing. Imagine if cells did not have a growth phase. What would happen to the size of daughter cells with progressive rounds of mitosis?
Think: What elsewould have tostop when thechromatin istightly coiled andcondensed intochromosomes formitosis? http://commons.wikimedia.org/wiki/File:Chromosome.svg
That’s right,transcription can’t bedone when the DNA istightly coiled.So Interphase is whenall of the cell’s geneticinstructions areprocessed. http://commons.wikimedia.org/wiki/File:Chromosome.svg
So, the chromosomes in the nucleus have been exactly copied See: Replication Core 3.4, AHL 7.2 During Prophase the Chromatin condenses into the familiar X shaped chromosome, which is actually two identical chromatids joined at the centromere. And then when the chromosomes split in half during anaphase, the identical chromatids are dragged to opposite ends of the cell Cytokinesis cuts the cell in half, with one set of duplicate DNA in one daughter cell and the other identical set in the other daughter cell ∴ Both nuclei are ∴ Both nuclei are identical identical http://www.flickr.com/photos/wellcomeimages/5987498303/http://w ww.flickr.com/photos/thejcb/4117622551/
2.5.6 State that growth, embryonic development, tissue repair and asexual reproduction involvemitosis Any time new cells are required, mitosis is required: • Growth: An 18 year old has many more cells than an 18 month old! • Embryonic development: You start as a zygote, one cell! • Tissue repair: Burnt, bashed, cut or eaten; dead or lost cells need to be replaced. • Asexual reproduction: In eukaryotes only remember: what do prokaryotes do?
Make your own Play Doh™ or Plasticine™ mitosis modelto further your understanding make your own playdough! http://www.flickr.com/search/?l=cc&mt=all&adv=1&w=all&q=mitosis&m=text
Further information: Three of the best sites for IB-specific Biology information. The top link takes you to the PPT by Stephen Taylor