2. Lecture 4 Outline (Ch. 12 & 13) I.Cell Cycle II.Cell Spindle & Mitosis A.Stages B.Plants vs. Animals III.Cell cycle controls IV.Genetics Overview V.Cell Reproduction VI.Karyotypes & Meiosis A.Stages B.Compare to mitosis VII.Independent Assortment VIII.Crossing-over/recombination IX.Lecture Concepts

3. Cell cycle overview -repeated -inputs, outputs -regenerative

4. cell cycle phases: G 1 – first gap S – DNA synthesis M – mitotic phase G 2 – second gap Interphase : G 1, S, G 2 mitosis & cytokinesis human cell – cycle ~24 hrs. M < 1hr, S ~10-12 hrs. Cell cycle phases

5. Cell Cycle Divide DNA Purpose of cell division? Divide cell Division to form sex cells: meiosis; gametes (sperm and egg) Division to duplicate body cells: mitosis; somatic cells - karyokinesis - cytokinesis -development -replacement two identical daughter cells

6. All organism’s genes = genome DNA Terminology chromosomes – packaged DNA Human genome ~ 30,000 genes ~ 3.2 billion nucleotides humans – 46 chromo, in 23 pairs – diploid (2n) most chromosomes – two “arms” – with centromere in middle

7. DNA duplication each chromosome copied - sister chromatids condense hugely chromosomes divided equally to daughter cells - attached at centromere

8. Mitosis How are chromosomes separated accurately? mitotic spindle - microtubules (MT) & assoc. proteins two poles of spindle MT radiate from centrosomes - MT organized - centrosome – centriole pair - astral MT - kinetochore MT - spindle MT

9. Before mitosis: Stages of Mitosis DNA duplicates centrosomes duplicate nucleus intact

10. Prophase DNA condenses nucleoli gone spindle forming Prophase Stages of Mitosis

11. ProphasePrometaphase nuclear membrane breaks spindle attaches DNA condensation Stages of Mitosis

12. PrometaphaseMetaphase centrosomes to ends kinetochores attach chromosomes line up Stages of Mitosis at metaphase plate

13. MetaphaseAnaphase sister chromatids separate kinetochore MT shorten spindle MT lengthen Stages of Mitosis

14. AnaphaseTelophase nuclear membrane reforms chromosomes decondense Stages of Mitosis

15. Stages of mitosis Cytokinesis begins during telophase completed after karyokinesis - cell membrane pinches in - actin fibers at midline - cleavage furrow

16. Self-Check 1 24 3 5 Arrange mitosis stages in order:

17. Mitosis in plant cells karyokinesis same in plant cells no centrioles, do have centrosomes cytokinesis different

18. cytokinesis different in plants: no cleavage furrow vesicles move on MT collect at midline – cell plate cell plate becomes cell wall Mitosis in plant cells

19. in dividing plant tissue – can find all stages of mitosis

20. transitions between phases? signals induce/promote cycle progression molecular control system Cell cycle controls

21. cycle proceeds until checkpoint three major checkpoints: G 1, G 2, M - critical stop vs. go choice Cell cycle controls

22. G 1 checkpoint critical G 1 “go ahead” – cell completes S, G 2, & M G 1 “no go” – cell exits cycle cells can return from G 0 and reenter cycle - non-dividing phase - G 0 Cell cycle checkpoints

23. checkpoints – signals 1. cyclin-dependent kinase (Cdk) 2. cyclin Cdk - persists, inactive w/out cyclin Cdk + cyclin = MPF cyclin – degraded, accumulates MPF – pass checkpoint Cell cycle checkpoints

24. G 2 checkpoint – regulated by MPF G 1 checkpoint – many Cdk s & cyclins M checkpoint – make sure all chromosomes attached before division Cell cycle checkpoints

25. Self-Check Fill in the chart above below each diagram with the stage of the cell cycle and what is happening (events) stageprophase eventsChromo condense CluesNuc intact Chromo copied

26. 1.Draw and label the cell cycle in order – include first checkpoint 2.Draw a cell in G 1 with 4 chromosomes; Draw a cell in metaphase with 4 chromosomes 3.Start with G 1 cell = 6 chromo; draw mitosis products Self-Check

28. heredity variation genetics locus – location along chromosome gene – unit of heredity Genetics overview - all genes from parents - your gene combination - study of heredity and heritable variation

29. asexual reproduction – mitotic division Cellular reproduction – clone – little variation sexual reproduction – two parents – gametes – unique combinations of gene variations

30. gametes – haploid (1n) – one chromosome set somatic cells – diploid (2n) – two sets; two parents karyotype – view of 2n set homologous chromosomes one from each parent autosomes vs. sex chromosomes Cellular reproduction

31. Karyotypes Chromosomes from human female cell

32. Karyotypes Aligned by homologues

33. cell preparing to undergo division: Meiosis - introduction sister chromatids centromere non-sister chromatids homologous chromosomes maternal paternal

34. Meiosis – overall goal two parts: meiosis I & II meiosis I – separate homologues meiosis II – separate sister chromatids reduce # of chromo 2n 1n input: one 2n cell output: four 1n cells

35. interphase Meiosis I prophase I -chromo replicate -centrosomes replicate -condense -synapsis -crossing over metaphase I anaphase I -metaphase plate -tetrads -homologues attached to MT -homologues separated

36. Meiosis I to Meiosis II telophase I & cytokinesis -sister chromatids attached -cell is haploid prophase II -no DNA replication prior -cells not identical

37. prophase II -sister chromatids metaphase plate metaphase II anaphase II telophase II & cytokinesis -MT attach to each chromatid -separate -four 1N cells, genetically distinct Meiosis II

38. Self-Check When does chromosome duplication occur? What is separated during meiosis I? “ “ meiosis II? “ “ mitosis?

39. Self-Check How many chromosomes? single or duplicated? one chromosome = chromatid sister chromatids tetrad non-sister chromatids

40. Mitosis vs. Meiosis no synapsis separate sister chromatids synapsis separate homologues separate sister chromatids 2n 1n

41. random arrangement of homologues = Independent assortment maternal paternal chance of getting paternal homologue: humans = 23 pairs 50% independent assortment 2 23, or ~ 8 million # of mat./pat. combinations?

42. Crossing-over prophase I - synapsis maternal paternal chromo align gene by gene crossing-over = swap bits of homologous DNA

43. meiosis creates haploid cells Life cycles gametes (sperm or eggs) gametes fuse = fertilization create zygote, diploid Human diversity: Independent assortment Crossing-over Random fertilization

44. Self-Check stage Prophase IMetaphase IAnaphase ITelophase I Prophase IIMetaphase II Anaphase II Telophase II events What to look for?

45. Lecture 4 concepts -Draw a diagram of the cell cycle – what happens at each step? -Recognize, describe, and order division stages for mitosis -Define ‘chromosome’, ‘karyokinesis’, ‘cytokinesis’, ‘sister chromatid’, ‘centromere’, ‘spindle’, ‘checkpoint’, ‘G 0 ’ -Know different types of spindle microtubules -Compare and contrast plant and animal cell division -Describe how cyclin and Cdk control checkpoint G2 -Recognize, describe, and order division stages for meiosis -Define ‘heredity’, ‘variation’, ‘gene’, ‘locus’, ‘chromosome’, ‘gamete’, ‘somatic’, ‘homologue’, ‘genetics’, ‘synapsis’ -Explain what a karyotype is and what it is used for -Compare and contrast asexual and sexual reproduction -Describe three BIG ways sexual reproduction provides genetic variation -Write out a list of new terminology and provide descriptions