1. Cell Reproduction and Division Ch 8

3. Chromosomes Chromosome: DNA wrapped upChromosome: DNA wrapped up w/ histones (proteins) = organized w/ histones (proteins) = organized Chromatin: uncoiled chromosome= unorganized DNA Chromatin: uncoiled chromosome= unorganized DNA

4. Chromosome # All species have their own characteristic # of chromosomes in each cellAll species have their own characteristic # of chromosomes in each cell

5. Chromosome Number Diploid 2n: pairs of chromosomes (1 from each parentDiploid 2n: pairs of chromosomes (1 from each parent Haploid 1n: unpaired chromosomes (sperm or egg)Haploid 1n: unpaired chromosomes (sperm or egg)

6. Chromosome Terminology 1 Chromosome With 2 chromatids (duplicated) 1 Chromosome 2 chromosomes (Unduplicated) 2 chromosomes (both duplicated) If these are homologous it is a tetrad Centromere

7. Chromosome Types SEX CHROMOSOMES Determine Gender –Males: XY –Females: XX –Male determines gender of the baby AUTOSOMES All non-sex chromosomesAll non-sex chromosomes

8. How many C’somes do you have? Humans: 23 pair = 46 chromosomesHumans: 23 pair = 46 chromosomes Karyotype: arrangement of an individuals chromosomesKaryotype: arrangement of an individuals chromosomes

9. Homologous Chromosomes Have the same type of information but with different detailsHave the same type of information but with different details #2 from mom has same kind of info as #2 from dad#2 from mom has same kind of info as #2 from dad Which ones aren’t homologous?Which ones aren’t homologous?

10. Haploid/Diploid

11. 25 Cell Division

12. Cell Division in Prokaryotes Binary Fission-Bacterial Cells reproduce asexuallyBinary Fission-Bacterial Cells reproduce asexually

13. Mitosis & Cell Division In Eukaryotes When a cell gets too big, it divides or stops growingWhen a cell gets too big, it divides or stops growing Eukaryotes first divide nucleus = Mitosis, then divide the rest = cytokinesisEukaryotes first divide nucleus = Mitosis, then divide the rest = cytokinesis

14. Cell Cycle A cells life is divided into a cycleA cells life is divided into a cycle Interphase, Mitosis & Cytokinesis are steps in the cycleInterphase, Mitosis & Cytokinesis are steps in the cycle

15. Stages of the cell cycle INTERPHASE = most active & majority of timeINTERPHASE = most active & majority of time – G1 stage = "GAP 1” - intense growth – S stage = "Synthesis” DNA replication occurs-IT DOUBLES!DNA replication occurs-IT DOUBLES! – G2 stage = "GAP 2” - duplicate organelles –G0 stage = exit cycle & never divide again (CNS=nerve cells) MITOSISMITOSIS – M stage = mitosis - nucleus divides Divided into PMATDivided into PMAT Cytokinesis = cell dividesCytokinesis = cell divides

16. Interphase The cell is metabolizing, growing and preparing for mitosisThe cell is metabolizing, growing and preparing for mitosis Chromosomes are not clearly seenChromosomes are not clearly seen Where a cell spends most of its lifeWhere a cell spends most of its life

17. Controlling the Cell Cycle Length variesLength varies 3 checkpoints based on proteins3 checkpoints based on proteins –G1, G2 and Mitosis Errors can lead to cancer.Errors can lead to cancer. –In cancer, regulation of the cell cycle is lost –Normal cell growth & behavior is lost.

18. What is Mitosis? Nuclear divisionNuclear division Produces two identical daughter cells during prophase, metaphase, anaphase, and telophase (PMAT).Produces two identical daughter cells during prophase, metaphase, anaphase, and telophase (PMAT).

19. Prophase= PREPARE for division, chromosome PRESENT Chromatin begins to condense and c’some becomes visible.Chromatin begins to condense and c’some becomes visible. Spindle fibers formSpindle fibers form

20. Prophase (cont.) Nuclear membrane dissolvesNuclear membrane dissolves Microtubules form mitotic spindleMicrotubules form mitotic spindle Kinetochore fibers and polar fibers attach to centromeresKinetochore fibers and polar fibers attach to centromeres

21. Metaphase-in MIDDLE Spindle fibers align the chromosomes in the center or equator of the cellSpindle fibers align the chromosomes in the center or equator of the cell Helps to ensure each new nucleus will receive one copy of each chromosome.Helps to ensure each new nucleus will receive one copy of each chromosome.

22. Anaphase-Chromatids APART Chromatids separate and move to opposite sidesChromatids separate and move to opposite sides Spindle fibers break downSpindle fibers break down Once separate they are called chromosomesOnce separate they are called chromosomes

23. Telophase-almost TW O cells Chromosomes arrive at opposite polesChromosomes arrive at opposite poles Nuclear envelope re-forms around daughter nuclei.Nuclear envelope re-forms around daughter nuclei. Chromosomes uncoilChromosomes uncoil Spindles disappearSpindles disappear

24. Cytokinesis in Animal Cells Cytoplasm is pinched (cleavage furrow) into two daughter cellsCytoplasm is pinched (cleavage furrow) into two daughter cells

25. Plants In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.

26. Meiosis - formation of gametes

27. Sexual Reproduction Sex cells divide by meiosis to produce haploid gamete (half the number of chromosomes)Sex cells divide by meiosis to produce haploid gamete (half the number of chromosomes) Gametes will join & fertilizeGametes will join & fertilize Meiosis produces 4 gametes that are slightly different in genetic makeup from each otherMeiosis produces 4 gametes that are slightly different in genetic makeup from each other Two gametes join to form 1 zygoteTwo gametes join to form 1 zygote

29. Meiosis I Reduces number of chromosomes by half (diploid to haploid) PMAT I’s – separate homologous pairsMeiosis I Reduces number of chromosomes by half (diploid to haploid) PMAT I’s – separate homologous pairs Meiosis II: Separates the sister chromatids PMAT II’sMeiosis II: Separates the sister chromatids PMAT II’s

30. Meiosis I

31. Meiosis II

32. Prophase I:Prophase I: –Synapsis (pairing of homologous c’somes) –When crossing-over happens (genetic recombination)

33. Crossing over: during Meiosis I Homologous pairs form tetrads, cross over and separate into individual chromosomesCrossing over: during Meiosis I Homologous pairs form tetrads, cross over and separate into individual chromosomes Homologous c’somes exchange genetic materialHomologous c’somes exchange genetic material Important for genetic diversityImportant for genetic diversity

34. Prophase I Each tetrad has two chromo- somes & fourchromatids

35. Meiosis Spermatogenesis: production of sperm cellsSpermatogenesis: production of sperm cells Oogenesis: production of egg cellsOogenesis: production of egg cells

36. Comparing Meiosis & Mitosis Genetic identity of progeny Mitosis Identical daughter cellsIdentical daughter cells diploiddiploid 1 cell  21 cell  2 Meiosis Daughter cells have new assortment of parental chromosomesDaughter cells have new assortment of parental chromosomes Chromatids not identical; crossing overChromatids not identical; crossing over Diploid to haploidDiploid to haploid 1 cell  41 cell  4

37. Sexual Reproduction Formation of offspring through meiosis and the union of a sperm and an egg (zygote)Formation of offspring through meiosis and the union of a sperm and an egg (zygote) Offspring are genetically different from parentsOffspring are genetically different from parents

38. Independent Assortment Anaphase I – homologous chromosomes separate from each otherAnaphase I – homologous chromosomes separate from each other Mendel figured this outMendel figured this out