Chapter 11 Eukaryotic Cell Cycle Cell Division I Eukaryotic Cell Cycle A Diagram 1 Time is not shown here 2 Cell moves clockwise through cycle starting at G1 B Interphase G1 S G2 Synthesis of DNA S Gap 1 G1 M Cytokinesis Gap 2 G2 1 G1 usually longest phase cells spend most of their life in G1 Mitosis a If cell stays in G1 forever it has exited the cycle and is in G0 G not i Can be turned on again b Cells in G1 or G0 are normally functioning cells doesn t mean they re dying 2 S DNA Synthesis Chromosome Replication Fig 11 4 3 G2 synthesize proteins for M phase C M Mitosis 1 Mitosis 2 Cytokinesis division of nuclear material genetic material Division of all other cellular material D Cell progression is controlled by cell signaling via Cyclin proteins 1 Involved at three checkpoints Fig 11 17 a End of G1 checkpoint is there DNA damage b End of G2 checkpoint is all the DNA replicated c Metaphase checkpoint are chromosomes attached to the spindle 2 Cyclins how they work Fig 11 14 1 1 1 1 Fig 11 4 a Amounts and types of cyclins vary as cell cycle progresses b Cyclins bind to turn on cyclin dependent kinases CDK s c CDK s phosphorylate activate proteins needed to continue in cycle d Cyclins are degraded when cell moves to next stage e Production of cyclin is the initial signal must be turned off eventually degraded II Fig 11 17 Eukaryotic Chromosome Structure Fig 11 14 A Chromosomes colored bodies 1 Units of genetic material made of chromatin contain genes a Chromatin mixture of protein histones DNA i Compacts DNA b Genes sequences of DNA that code for a product the DNA regions that control production start stop codons promoter etc B Structure Fig 11 4 pages 1 3 1 Eukaryotic chromosomes are linear a Centromere region of constriction i Doesn t have to be in the middle 2 After chromosome replication DNA get pushed pulled around C Chromosomes occur in sets a Pair of sister chromatids 1 chromosome even though you now have double the b Kinetochore proteins lie over the centromere region interact with microtubules 1 Haploid a 1 copy of each type of chromosome n b Gametes of diploid organisms are N haploid c Haploid organisms produce gametes by mitosis autosomal cells and gametes are 1 2 both N 2 Diploid a 2 copies of each chromosome 2N b Autosomal non gametic cells of diploid organisms are 2N c Gametes are N 3 Some eukaryotes are tetraploids 4N a Ex Durum wheat green treefrog 1 1 2 2 III Mitosis A Forms 2 genetically identical daughter cells B S Phase occurs before any of mitosis Fig 11 4 C 5 phases of Mitosis PPMAT I Fig 11 5 1 Prophase a Chromosomes condense b Dark Blue paternal copy c Light Blue maternal copy 2 Prometaphase a Nuclear membrane breaks down b Spindle forms c Microtubules attach to kinetochore proteins of chromosomes Fig 11 6 a Sister chromatids align on metaphase 3 Metaphase Fig 11 4 plate poles 4 Anaphase a Sister chromatids separate move to 5 Telophase cytokinesis a Nuclear membrane reforms daughter 6 cells separate Interphase a Chromosomes replicate S Required for mitosis to occur Fig 11 6 IV Meiosis Fig 11 5 A Reduction division I e N daughter cell produced from 2N parent cell 1 2 2 rounds of division Meiosis I Meiosis II 3 Same steps as mitosis done twice Some differences B Unique to Meiosis I Fig 11 9 1 Homologous chromosomes already duplicated synapse pair to form bivalents or tetrads 2 Synapsed chromosomes exchange some material crossing over 3 At the site of crossover the chromosomes form an X or 4 chiasma In eukaryotes 1 60 crossovers occur per chromosome per meiosis C Meiosis I Fig 11 10 1 5 Phases a Prophase I b Prometaphase I c Metaphase I d Anaphase I e Telophase I Fig 11 8 tetrads form crossing over bivalents attach to microtubules bivalents randomly align on plate homologous chromosomes move to separate poles haploid daughter cells separate 2 Meiosis I is reduction division 2 haploid cells from 1 diploid 3 2 processes increase genetic diversity in Meiosis I a Crossing over prophase I b Random alignment of chromosomes on metaphase plate metaphase I Fig 11 9 Fig 11 10 Meiosis I Fig 11 8 Prophase I D Meiosis II Fig 11 11 1 Prophase II 2 Prometaphase II 3 Metaphase II 4 Anaphase II 5 Telophase II no tetrads or crossing over sister chromatids attach to microtubules sister chromatids align on plate sister chromatids separate chromosomes move to separate poles cleavage 4 haploid cells produced V Mitosis vs Meiosis EVENT Tetrads form Crossing over occurs What aligns on metaphase plate What is produced Mitosis No No Sister chromatids 2 cells diploid Reduction Division No Meiosis I Yes Yes Tetrads bivalents 2 cells haploid with sister chromatids Yes Meiosis II Yes No Sister chromatids 4 cells haploid No
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