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Biology is the only subject in which multiplication is the same thing as division… Regents Biology 2006-2007 MITOSIS: Making New Cells Making New DNA Regents Biology Where it all began… You started as a cell smaller than a period at the end of a sentence… Regents Biology And now look at you… Regents Biology How did you get from there to here? Getting from there to here… Going from egg to baby…. the original fertilized egg (zygote) has to divide… and divide… and divide… and divide… Regents Biology Binary fission Why do cells divide… One-celled organisms for reproduction asexual reproduction (clones) amoeba Multi-celled organisms for growth & development from fertilized egg to adult for repair & replacement replace cells that die from normal wear & tear or from injury Regents Biology starfish regeneration Examples of Asexual Reproduction Binary Fission is the equal division of both the organism’s cytoplasm and nucleus to form two identical organisms Budding involves one parent dividing its nucleus (genetic material) equally, but cytoplasm unequally yeast Regents Biology protist Regents Biology Regents Biology Sporulation (spore formation) reproduction involving specialized single cells coming from one parent Regents Biology Regeneration Grafting Regents Biology Asexual Reproduction Advantages Genetic continuity Faster Do not need a mate Disadvantages If environmental conditions change, may die out Disease could eliminate the population Regents Biology Dividing cells… What has to be copied DNA organelles cell membrane lots of other molecules enzymes Regents Biology plant cell animal cell Copying DNA A dividing cell duplicates its DNA creates 2 copies of all DNA separates the 2 copies to opposite ends of the cell splits into 2 daughter cells DNA cell Regents Biology nucleus But the DNA starts loosely wound in the nucleus If you tried to divide it like that, it could tangle & break Organizing & packaging DNA DNA (chromatin) cell nucleus DNA has been “wound up” DNA in chromosomes in everyday “working” cell cell nucleus 4 chromosomes in thisBiology organism Regents DNA in chromosomes in cell getting ready to divide Chromosomes of Human Female 46 chromosomes 23 pairs Regents Biology Chromosomes of Human Male 46 chromosomes 23 pairs Regents Biology Copying & packaging DNA When cell is ready to divide… copy DNA first, then… coil up doubled chromosomes like thread on a spool… now can move DNA around cell without having it tangle & break Regents Biology Copying DNA Coil DNA into compact chromosomes What happens when DNA breaks? Mutations which can lead to…….. Cancer – uncontrolled cell growth melanoma Regents Biology double-stranded human chromosomes ready for mitosis Regents Biology DNA must be duplicated… chromosomes in cell DNA in chromosomes cell nucleus 4 single-stranded chromosomes duplicated chromosomes duplicated chromosomes Biology chromosomes 4Regents double-stranded cell nucleus INTERPHASE CELL IS GROWING CHROMOSOMES ARE REPLICATED (COPIED) Regents Biology PROPHASE 1. CHROMATIN BECOMES 2. 3. 4. 5. 6. CONDENSED (THICKER) NUCLEOLUS DISAPPEARS NUCLEAR MEMBRANE DISAPPEARS CENTRIOLES BEGIN TO MOVE TOWARDS THE POLES SPINDLE FIBERS START TO APPEAR CHROMOSOMES BECOME VISIBLE Regents Biology METAPHASE CHROMOSOMES LINE UP ALONG THE MIDDLE OF CELL Regents Biology ANAPHASE CENTROMERES SPLIT ALLOWING CHROMATIDS TO SEPARATE ONE MATCHING CHROMATID MOVES TO EACH POLE Regents Biology Regents Biology TELOPHASE AND CYTOKINESIS CHROMATIDS AT OPPOSITE POLES SPINDLE FIBERS DISAPPEAR NUCLEAR MEMBRANE REAPPEARS CYTOKINESIS: CELL DIVIDES INTO TWO GENETICALLY IDENTICAL CELLS Regents Biology New “daughter” cells Get 2 exact copies of original cells same DNA “clones” Regents Biology Regents Biology Cell division in Animals Regents Biology Mitosis in whitefish embryo Regents Biology onion root tip Regents Biology KEYS TO MITOSIS Original cell has complete set of chromosomes This is known as DIPLOID or 2N No genetic material exchanged Cells are GENETICALLY IDENTICAL Daughter Cells are also DIPLOID or 2N One division results in 2 DAUGHTER CELLS Ex. Original cell has 46 chromosomes, daughter cells will have 46 chromosomes IN SINGLE CELLED ORGANISMS: Method of reproduction (ASEXUAL) Protists, some Algae, and Molds IN MULTI-CELLED ORGANISMS: Mitosis used for GROWTH and REPLACEMENT of BODY CELLS (skin, liver, heart etc…) Regents Biology Overview of mitosis interphase I.P.M.A.T.C. prophase Please Make Another Two Cells cytokinesis Regents Biology metaphase anaphase telophase Basic diagram of mitosis HUMAN SKIN CELL 46 Chromosomes 46 Chromosomes Regents Biology 2 NEW HUMAN SKIN CELLS 46 Chromosomes