IB Biology 2 Cells 2.5 Cell Division
All syllabus statements ©IBO 2007 All images CC or public domain or link to original material. Adapted from Jason De Nys PowerPoint hGp://commons.wikimedia.org/wiki/File:Scotchquaileggs.jpg Why do cells divide? What is the life cycle of a cell? Produce a pie-­‐chart of the stages by using this online lab: hGp://www.biology.arizona.edu/cell_bio/acSviSes/cell_cycle/cell_cycle.html
Observe on the real onion root-­‐Sp, too. 2.5.1 Outline the stages of the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis Interphase is the longest porSon of a cell’s life and has three subdivisions: First Gap G1 hGp://commons.wikimedia.org/wiki/File:First_gap_cell_lifecycle.svg Synthesis S hGp://commons.wikimedia.org/wiki/File:Synthesis_cell_lifecycle.svg Second Gap G2 hGp://commons.wikimedia.org/wiki/File:Second_gap_cell_lifecycle.svg Detail in 2.5.4 hGp://commons.wikimedia.org/wiki/File:Prophase_procarioSc_mitosis.svg Gp://commons.wikimedia.org/wiki/File:Metaphase_procarioSc_mitosis.svg commons.wikimedia.org/wiki/File:Anaphase_procarioSc_mitosis.svghGp://
commons.wikimedia.org/wiki/File:Telophase_procarioSc_mitosis.svg Mitosis:
The cell divides it’s chromosomes into 2 idenScal sets 4 Main stages Cytokinesis hGp://commons.wikimedia.org/wiki/File:Cytokinesis_eukaryoSc_mitosis.svg Stage Gap 1 (G1) Events •  Protein Synthesis •  Organelles produced •  Cytoplasm increases in size Synthesis (S) DNA is duplicated •  Organelles produced Gap 2 (G2) •  Cytoplasm increases in size Mitosis The cell divides it’s chromosomes into two idenScal sets 4 Stages •  Prophase •  Metaphase •  Anaphase •  Telophase Cytokinesis 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 can occur in any organ or Sssue. In cancerous cells, control of mitosis has been lost and they divide… and divide… and divide. This leads to tumours (cancer Sssue) that displaces healthy Sssue and interferes with proper funcSon. Cancer can arise from any cells capable of mitosis Background: A Brenner tumour in an ovary. These are usually benign, but can be malignant hGp://commons.wikimedia.org/wiki/File:Brenner_tumour_intermed_mag.jpg It’s too late to apopAse!
2.5.3 State that interphase is an acSve period in the life of the cell when many metabolic reacSons occur, including protein synthesis, DNA replicaSon, and an increase in the number of mitochondria and chloroplasts. State: give a specific name, value or other brief answer without explanaSon or calculaSon The name ‘interphase’ implies a period of Sme 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 funcSons 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 else would have to stop when the chromaSn is Sghtly coiled and condensed into chromosomes for mitosis? hGp://commons.wikimedia.org/wiki/File:Chromosome.svg That’s right, transcripSon can’t be done when the DNA is Sghtly coiled. So Interphase is when all of the cell’s geneSc instrucSons are processed. hGp://commons.wikimedia.org/wiki/File:Chromosome.svg Extension: hGp://www.flickr.com/photos/seyyed_mostafa_zamani/4266283238/ 2.5.4 Describe the events that occur in the four stages of mitosis ^C Prophase Metaphase Anaphase Telophase First 3D video of mitosis. Source forgoGen, let me know if you know! Pea MAT hGp://www.flickr.com/photos/cmatsuoka/3732303102/ hGp://www.flickr.com/photos/zaser/2524931166/ People Meet And Talk hGp://www.flickr.com/photos/chuckp/252924532/ 2.5.5 Explain how mitosis produces two geneScally idenScal nuclei Think back to slide 4… What happens during the synthesis part of interphase? Synthesis S hGp://commons.wikimedia.org/wiki/File:Synthesis_cell_lifecycle.svg So, the chromosomes in the nucleus have been exactly copied See: ReplicaSon Core 3.4, AHL 7.2 During Prophase the ChromaSn condenses into the familiar X shaped chromosome, which is actually two idenScal chromaSds joined at the centromere. And then when the chromosomes split in half during anaphase, the idenScal chromaSds 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 idenScal set in the other daughter cell ∴ Both nuclei are idenAcal ∴ Both nuclei are idenAcal hGp://www.flickr.com/photos/wellcomeimages/5987498303/hGp://
www.flickr.com/photos/thejcb/4117622551/ 2.5.6 State that growth, embryonic development, Sssue repair and asexual reproducSon involve mitosis Any Ame 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 reproducAon: In eukaryotes only remember: what do prokaryotes do? Make your own Play Doh™ or PlasAcine™ mitosis model to further your understanding make your own playdough! hGp://www.flickr.com/search/?l=cc&mt=all&adv=1&w=all&q=mitosis&m=text Further informaSon: Anim
aSon
by Jo
hn Ky
rk Three of the best sites for IB-­‐specific Biology informaSon. The top link takes you to the PPT by Stephen Taylor