Development Including Mitosis and Meiosis

1. Development Including Mitosis and Meiosis A. Russo-Neustadt CSULA

7. Lancelet early development

9. I. The Cell Cycle Division of cytoplasm and organelles between new cells G = gap IPMAT M = mitosis or meiosis, DNA is divided between two new cells Regular sequence of events in which a cell grows and carries out regular activities, prepares to divide and then divides to produce two new cells

10. Mitosis A. Results in 2 new cells with the same # of chromosomes as the original cell Meiosis A. Results in 4 new cells each with ½ the # of chromosomes as the original cell II. Comparison of Mitosis and Meiosis 2n = diploid cell 2n cell 4 X 1n = haploid cells 2 X 2n cells

11. Mitosis B. Cytokinesis is usually approximately equal C. Used for – growth repair development (embryogenesis) asexual reproduction Meiosis B. Cytokinesis can be unequal (oogenesis) C. Used for – gametogenesis II. Comparison of Mitosis and Meiosis - continued

12. Definitions Chromosome = DNA and its associated proteins, 46 in humans Homologous chromosomes = chromosomes that contain information to control the same genetic trait, one member of each pair came from mom and one came from dad

13. Definitions – continued: Site where sister chromatids are held together, microtubules of spindle apparatus attach here during cell division Copies of the same chromosome that result from S phase

14. Definitions – continued: Equator = center plane of the cell Spindle apparatus = portion of the cytoskeleton that orients and separates sister chromatids or homologous chromosomes during cell division; contains poles and microtubules

22. How is Diversity achieved? CROSSING OVER INDEPENDENT ASSORTMENT

23. LET’S REVIEWif time permits

24. Steps in Development • Gametogenesis = production of gametes through the process of meiosis • Spermatogenesis = sperm cell production 2 meiotic divisions 2n 1n 1n 1n 1n 2n (diploid) testis cell 4 X 1n (haploid) sperm cells

25. A. Gametogenesis - continued B. Oogenesis = egg cell production 2 meiotic divisions 1n 2n 1n 1n 1n 2n (diploid) follicle cell 1 haploid (1n) egg + 3 haploid polar bodies Gets all the cytoplasm and organelles at cytokinesis essentially 3 haploid nuclei that are discarded

26. B. Fertilization The union of an egg cell and a sperm cell that produces a zygote (fertile egg) and re-establishes the diploid condition fusion 1n 2n egg zygote 1n sperm

27. C. Embryogenesis embryo formation: consists of cleavage + gastrulation + organ formation All three steps will make use of mitosis to produce new cells

28. 1. Cleavage = division of the single celled zygote into a many celled structure called a blastula (hollow ball of cells); uses mitosis so that all cells in the developing animal will have a complete set of genes Requires multiple mitotic divisions 2n 2n 2n Fluid-filled 2n 2n X.S.

29. 2. Gastrulation = transformation using complex cell movements of a blastula into a multi-layered animal (gastrula); mitotic cell division continues as developing animal continues to increase in size Breaks through to form mouth or anus l.s. gut becomes mouth or anus x.s. gut All cells are 2n

30. 3. Organ Formation Differentiation and specialization of embryonic tissues (endoderm, ectoderm and mesoderm) into adult tissues (epithelial, connective, muscle and nervous tissues) and organs

31. Final Steps in Development D. Growth = increase in size; differentiation usually continues E. Maturation = attainment of adult body form capable of reproduction metamorphosis as an example of a dramatic maturation process