1. Cell Reproduction: Mitosis and Meiosis Big Idea # 3 Genetics and Information Transfer

2. Cell Tissue Organism Population Ecosystem How does the process effect each level of organization?

3. Terms Anaphase Binary fission Cancer Cell cycle Cell plate Checkpoint Chromatin Chromosome Crossing over Cleavage furrow Cyclin Cyclin-dependent kinase (Cdk) Cytokinesis Density dependent inhibition Diploid

4. G 0 G 1 G 2 Gamete Genome Haploid Homologous chromosomes Interphase M phase Meiosis Metaphase Mitosis MPF PDGF Prophase S phase Sister chromatids Somatic cell Telophase

5. BIG Idea # 3 Genetics and Information Transfer 3.A.2 – The Cell Cycle Is A complex Set of Stages That Is Highly Regulated With Checkpoints, Which Determines the Ultimate Fate of the Cell

6. Cell Cycle

7. 3.A.2 – The Cell Cycle Is a Complex Set of Stages Mitosis passes a genome from the parent cells to daughter cells –Mitosis occurs after DNA replication –Produces two identical cells –Growth, repair, asexual reproduction –Continuous process with observable structures (order of the processes – replication, alignment, separation) Mitosis alternates with interphase

8. Genome All the genes of an organism Genes – sections of DNA with code for making proteins –Humans - 25,000 genes*, 46 chromosomes –Average gene - 3000 nucleotides

9. Cell Division Prokaryote – circular DNA –Bacteria divide by binary fission –No coiling of DNA –No proteins to manage the DNA Eukaryote = DNA coils into multiple chromosomes –DNA ‘managed’ by proteins

10. Plasma membrane grows inward Mitochondria and chloroplasts go through similar processes Binary Fission in Bacteria

11. DNA is making proteins most of the time Chromatin - DNA + proteins (histones) Before mitosis, chromatin is replicated; chromatin condenses, coils and folds into a chromosome Eukaryotes - Chromatin

12. Chromosomes Chromosome = two sister chromatids connected by a centromere Chromatids are pulled apart into two new cells at the end of mitosis/meiosis

13. Homologous Pairs

14. Chromosomes Each species has a characteristic number of chromosomes –Human somatic cells have 46 (diploid) –Human gametes have 23 (haploid) Karyotype – arrangement of chromosomes

15. 3.A.2 – The Cell Cycle Is a Complex Set of Stages After specialization, a cell enters a non-dividing state but may re-enter the cell cycle when given appropriate cues Interphase - three phases –Growth –Synthesis –Preparation for mitosis

16. Interphase - cell growth –Longest time of the cycle –Three subphases: G 1 (“first gap”) growth S (“synthesis”) DNA is copied G 2 (“second gap”) cell completes preparations for division G 0 – some cells do not re-enter ‘S’ Cell Cycle

17. The cell cycle is directed by internal control or checkpoints internal and external signals provide stop-and-go signs at the checkpoints. –MPF –Platelet-derived growth factor (PDGF) –Cancer results from disruptions of the cycle controls –Cyclins and cyclin-dependent kinases control the cell cycle 3.A.2 – The Cell Cycle Is a Complex Set of Stages

18. Frequency of cell division depends on the type of cell –Skin cells - frequent –Liver cells do not divide unless damaged (G o ) –Nerve and muscle cells do not divide after maturity (permanent G o ) Cell cycle is controlled by chemical signals: –Evidence: fuse a cell in S phase with a cell in G 1, the G 1 cell will start S –Evidence: fuse a cell in mitosis with one in interphase causes the cell in interphase to start mitosis Regulation of the Cell Cycle

19. Cell Cycle Control Checkpoints in cycle are control points –Checks to be sure all ‘steps’ are completed –Hormone signals from outside also help control the cycle 3 checkpoints; G 1, G 2, and M phases

20. Cell Signaling

21. Cell Cycle Control G 1 checkpoint (restriction point) is most important –G o signal = completes cell cycle and divides –No G o = cell exits cycle

22. Cell Cycle Control Rhythmic fluctuations of proteins controls the cycle –Kinases - activate or deactivate other proteins Constant amount –Cyclins – levels fluctuate Kinases and cyclin form cyclin-dependent kinases (Cdks)

23. Cyclin increases during interphase, then decreases during mitosis MPF – composed of cyclin-Cdk –“Maturation-Promoting Factor” triggers cell past G 2 checkpoint to M phase Cell Cycle Control

24. Internal and External Cues M phase checkpoint - ensures that the chromosomes are attached to the spindle at metaphase plate before anaphase begins so that daughter cells do not end up with missing or extra chromosomes –APF

25. Mitosis is a continuous process: –Mitosis is ‘usually’ broken into four subphases: Prophase Metaphase Anaphase Telophase

26. Prophase - Formation Chromatin coils up to form chromosomes G 2 checkpoint –MPF builds to a peak Metaphase - Alignment Spindle fibers push the chromatids until they are all arranged at the metaphase plate M – phase checkpoint – –APF builds up, MPF degrades

27. Anaphase - Separation Centromeres divide –Separates chromatids Each chromatid is pulled toward the pole by spindle fibers Telophase : Cell elongates Two nuclei envelopes begin to reform Chromatin uncoils Cytokinesis begins

28. Animal cells: –Cleavage furrow - contractile ring of actin and myosin forms Plants have cell walls –Cell plate - vesicles from Golgi coalesce at the metaphase plate –Plate enlarges until fused with the plasma membrane Cytokinesis

29. Density-dependent inhibition –Normal cultured cells divide until they form a single layer –Cells will grow to fill a gap Anchorage dependence – cells must be anchored (extracellular matrix) Internal and External Cues

30. Do not respond to density-dependent inhibition or anchorage dependence Do not stop dividing when growth factors run out May be ‘immortal’ –Normal cells - 20 to 50 times in vitro –HeLa cells - Henrietta Lacks Cancer Cells

31. Terms Allele Chromosome Crossing over Fertilization Gamete Gametogenesis Gene Locus Meiosis I Meiosis II Sex chromosome Sexual reproduction Synapsis Tetrad Zygote

32. Meiosis, a reduction division followed by fertilization, ensures genetic diversity in sexually reproducing organisms –Ensures each gamete receives one complete haploid (1n) set of chromosomes –Homologous chromosomes are paired with one homologue originating from the maternal parent and one from the paternal parent. Orientation of the chromosome pairs is random with respect to the cell poles –Separation of the homologous chromosomes ensures that each gamete receives a haploid set of chromosomes composed of both maternal and paternal chromosomes

33. –Homologous chromosomes may exchange genetic material via ‘crossing over’ which increases genetic variation –Fertilization involves the fusion of two gametes increasing genetic variation in populations by providing for new combinations of genetic information in the zygote and restores the diploid number of chromosomes

34. Asexual Reproduction Single parent No genetic variation –Cloning, plant cuttings –Binary fission in bacteria –Spores – plants, fungi Very rapid, energy efficient method Few mutations - ‘bad’ or ‘weak’ genes also passed along Genes susceptible to environmental change

35. Sexual Reproduction Sexual reproduction: –Requires more energy –Slower –Gametogenesis - meiosis Genetic variation*** Survival of the fittest

36. Somatic cell - any cell other than gamete Gamete - sex cell, haploid

37. Homologous Chromosomes Homologues - same size, same genes Same gene loci – location of gene on the chromosome Autosome - non-sex chromosomes (22 pairs) Sex chromosome – carries gene that determines gender; dissimilar

38. Heredity: Meiosis Mitosis : 4 stages 2 identical daughter cells Diploid (2n) Meiosis : 8 stages 4 non-identical cells Haploid (1n)

41. Meiosis – Crossing Over Prophase I: Synapsis - homologous chromosomes come together as pairs Tetrads Crossing over may occur

42. Nondisjunction Chromatids fail to separate during meiosis Gametes are ANEUPLOID (have incorrect number of chromosomes)