2.5 Cell Division As seen in eukaryotes

Cell cycle The life of a cell Events between cell division Needed for cell growth, tissue repair, and cell maintenance Produces two genetically identical nuclei

Cell Cycle Overview Interphase: G1, S, G2 Mitosis: Prophase – DNA (chromatin) condenses Metaphase – chromosomes align on equator Anaphase – chromatids separate, move to opposite poles Telophase – 2 genetically identical nuclei form Cytokinesis - cytoplasm divides cytokinesis

Interphase: G1: metabolic reactions, cell growth, cell performs its function(s), transcription and translation of useful genes to make proteins

Interphase: S : Replication (all DNA is copied) G2: some growth, production of molecules needed for mitosis At any time during interphase, chloroplasts and mitochondria can reproduce by simple division. Some cells can stay in interphase forever.

DNA vocabulary: Both are chromosomes This one has 2 chromatids (indentical). As soon as they separate at the centromere, they will be separate chromosomes. Uncondensed chromosomes are called chromatin

Prophase: DNA supercoils into chromosomes. Spindle microtubules assemble (grow from poles) Centrioles move toward poles Nuclear membrane breaks down

Metaphase Spindle microtubules attach to centromeres Chromosomes line up along equator

Anaphase Spindle microtubules shorten Sister chromatids split into identical chromosomes Chromosomes are pulled to opposite poles

Telophase Chromosomes uncoil at poles Nuclear membrane reforms Spindle microtubules break down Daughter cells enter interphase

Cytokinesis The cytoplasm divides in two May happen at the same time as telophase; may not happen at all (muscle).

Mitosis produces genetically identical nuclei Mitosis animation Mitosis animation with cell movieMitosis animation with cell movie

Mitosis forms cells for: Asexual reproduction Embryonic development Growth Tissue repair

Cancer: Uncontrolled Cell Cycle Repeated, rapid divisions Ignores body signals (growth inhibitors) Creates growing group of out-of- control cells (tumour) Tumours can be in any organ Tumours can spread throughout the body (metastasize) Abnormal numbers of chromosomes develop from rushed division

Fighting Cancer Cancer treatments like radiation and some chemotherapy drugs target rapidly dividing cells for destruction. This causes hair to fall out and damage to the intestinal lining causing nausea, because these cells also divide rapidly New treatments try to target cancer cells more specifically.

Lab: Mitosis in Onion Root Tips See lab handout

Homework Pg. 40 #1-6