Mitosis The division of the nucleus 2016 Paul

Conception All animals begin as a fertilised egg cell (a zygote) www. overpopulation. org/WOAimages/zygote_nice.

Then it divides… www. ehd. org/images/gasserbook/Gasser_Fig 1 -2 gs. jpg © 2016 Paul Billiet

… and divides www. coloradospringsivf. com/img/progeny/5. jpg © 2016 Paul Billiet ODWS

Until it becomes an embryo www. scienceclarified. com/. . . /uesc_04_img 0230. jpg ©

But what actually happens when a cell divides? l l l http: //www. johnkyrk.

Interphase (plant cell) © 2016 Paul Billiet ODWS

Interphase: In between cell divisions Centriole Cytoplasm Nucleus Plasma membrane Nucleus envelope Nucleolus The

Prophase: Division begins Centriole divides Threads appear in the nucleus = Chromosomes condensing Nucleus

End of prophase: The nucleus disappears l Nucleus envelope breaks down Spindle fibres grow

Metaphase: The chromosomes are organised l l Chromosomes line up across the equator of

Anaphase: The chromosomes split l l The sister chromatids of each chromosome split The

Telophase: The end of mitosis l l The nuclei reform Each one contains a

Using confocal microscopy © 2016 Paul Billiet ODWS

Plant v Animal cells l l Centriole Cytokinesis: Cell plate v cleavage © 2016

Chromosomes and cell division l l Multicellular organisms copy their chromosomes before cell division

The cell cycle Cytokinesis division of the cytoplasm M G 0 Some cells may

Cell cycles are not uniform Cell type Bean root tip Cell cycle / h

Cyclins help control cell division l l l Cyclins are proteins Cyclins are expressed

Cyclins and the cell cycle © 2016 Paul Billiet ODWS

Cancer l l l Mutation of regulatory genes (oncogenes) Uncontrolled cell division primary tumour

Cancer and cyclins MUTOGENS Cyclins synthesized CDK activated Regulatory proteins phosphorylated eg retinoblastoma protein

Cancer cells v normal cells l https: //www. youtube. com/watch? v=Pwq. Y 99 g

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But what actually happens when a cell divides? l l l http: //www. johnkyrk. com/mitosis. html https: //www. youtube. com/watch? v=DD 3 IQkn. CEdc https: //www. youtube. com/watch? v=s 1 yl. UTb. Xy. WU https: //www. youtube. com/watch? v=a. DAw 2 Zg 4 Ig. E http: //blogs. scientificamerican. com/observations/2 014/10/23/movies-made-inside-a-living-cell-video/ © 2016 Paul Billiet ODWS

Interphase: In between cell divisions Centriole Cytoplasm Nucleus Plasma membrane Nucleus envelope Nucleolus The working cell l It grows in size (protein synthesis) l It copies its genetic material (replication) © 2016 Paul Billiet ODWS

End of prophase: The nucleus disappears l Nucleus envelope breaks down Spindle fibres grow out from the ends of the cell l Chromosomes appear as two threads (the chromatids) joined by a constriction (the centromere) © 2016 Paul Billiet ODWS Sister chromatids Centromere

Telophase: The end of mitosis l l The nuclei reform Each one contains a complete set of chromosomes A new nuclear envelop forms The chromosomes uncoil l The cytoplasm divides in two to form two identical daughter cells l The cells goes back to work © 2016 Paul Billiet ODWS

Chromosomes and cell division l l Multicellular organisms copy their chromosomes before cell division The cells must grow to a mature size Interphase The nucleus divides, distributing the chromosomes into two equal groups Mitosis The cytoplasm then divides each part taking a nucleus Cytokinesis © 2016 Paul Billiet ODWS

The cell cycle Cytokinesis division of the cytoplasm M G 0 Some cells may stay in this stage for over a year First growth phase. Varies in length G 1 G 2 Second growth period S Copying of chromosomes G 1 + S + G 2 = INTERPHASE © 2016 Paul Billiet ODWS

Cell cycles are not uniform Cell type Bean root tip Cell cycle / h 19. 3 Mouse fibroblast 22 Chinese hamster fibroblast 11 Mouse small intestine epithelium 17 Mouse oesophagus epithelium 181 © 2016 Paul Billiet ODWS

Cyclins help control cell division l l l Cyclins are proteins Cyclins are expressed during different stages of the cell cycle Interact with cyclin dependent kinases (CDK) CDKs phosphorylate other molecules The phosphorylated molecules bring about changes in the activity of the cell Cyclins rise and fall at critical points in the cell cycle © 2016 Paul Billiet ODWS

Cancer l l l Mutation of regulatory genes (oncogenes) Uncontrolled cell division primary tumour Metastasis secondary tumour.