Lesson 1. Cell cycle Chromosomes Mitosis phases

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1 Lesson 1 Cell cycle Chromosomes Mitosis phases

5 Organism Diploid chromosome # (2n) in body cells Haploid chromosome # (n) in gametes Human *(memorize) Goat Guinea pig Bat Squirrel Alligator Chicken King crab Fruit fly 8 4 Pea 14 7 Apple Potato Soybean Lettuce 18 9 Rice Leopard Frog 26 13

7 Lesson 2 Meiosis phases

8 Metaphase Prophase Anaphase Telophase I I I I

9 Prophase II Telophase II Anaphase II Metaphase II

10 Cells can divide in two different ways MITOSIS MEIOSIS

11 Organism Diploid chromosome # (2n) in body cells Haploid chromosome # (n) in gametes Human *(memorize) Goat Guinea pig Bat Squirrel Alligator Chicken King crab Fruit fly 8 4 Pea 14 7 Apple Potato Soybean Lettuce 18 9 Rice Leopard Frog

12 Meiosis I Metaphase I Anaphase I 12

13 Meiosis II Metaphase II Anaphase II 13

14 In what types of cells does it occur? Comparison Chart Mitosis Meiosis What type of reproduction is this process involved in? How many divisions occur? Number of daughter cells produced? Chromosome number of daughter cells produced? Genetic comparison with the original cell? Does crossing over occur? 14

15 Comparison of Mitosis and Meiosis Table

16 Meiosis Cell division that produces gametes with half the number of chromosomes Occurs in special cells called germline cells found in the gonads Maintains the chromosome number of a species over generations via fertilization Ensures genetic variability via the processes of independent assortment and crossing over of chromosomes 16

17 Meiosis consists of two divisions - Meiosis I = The reduction division - Reduces the number of chromosomes from 46 to 23 - Meiosis II = The equational division - Produces four cells from the two produced in Meiosis I Note: Each division has the 4 phases (PMAT) Prophase, Metaphase, Anaphase, Telophase 17

18 Meiosis

19 Meiosis I

20 Prophase I Homologs pair-up and undergo crossing over Chromosomes condense Spindle forms Nuclear envelope/membrane breaks down

21 Crossing-over Paired chromosomes (homologs) exchange genetic information resulting in genetic variation in each gamete produced Occurs during synapsis in Prophase I

22 Metaphase I Homologous pairs align along the cell s equator Random alignment pattern determines the independent assortment of chromosomes in the gametes

23 Independent Assortment

24 Anaphase I Homologs separate and move to opposite poles of the cell Sister chromatids remain attached at their centromeres

25 Telophase I Nuclear envelope reforms Spindle disappears Cytokinesis divides the rest of the cell into two

26 Interkinesis A short interphase between the two meiotic divisions Chromosomes unfold into very thin threads Proteins are manufactured However, DNA is NOT replicated a second time

27 Meiosis II (same as Mitosis)

28 Prophase II Chromosomes condense and become visible again Spindles form Metaphase II Chromosomes align along the equator Nuclear envelope degenerates

29 Anaphase II Centromeres divide Sister chromatids separate to opposite cell poles Telophase II Nuclear envelope reforms Chromosom es uncoil Spindle disappears

30 Results of Meiosis Four haploid cells containing a single copy of the genome (23 chromosomes each) Each cell is unique carries a different assortment of genes and chromosomes

31 Lesson 3 Gametogenesis - spermatogenesis - oogenesis

32 Gametogenesis The process in which cells undergo meiosis to form gametes

33 Spermatogenesis

34 Spermatogenesis Occurs in the seminiferous tubules of the testes, beginning at puberty continuing throughout the man s life A diploid spermatogonium divides by mitosis to produce a stem cell and another cell that specializes into a primary spermatocyte In meiosis I, the primary spermatocyte produces two haploid secondary spermatocytes In meiosis II, each secondary spermatocyte produces two haploid spermatids Spermatids then mature into tad-pole shaped spermatozoa (4 sperm cells in total)

35 Spermatogenesis

36 36

37 Sperm Structure Acrosome contains digestive enzymes to help penetrate egg Mitochondria provide energy Tail provides motility

38 Oogenesis

39 Oogenesis Unlike spermatogenesis, oogenesis is a discontinuous process Meiosis begins during fetal development of female Oocytes pause development at prophase I until puberty After puberty, meiosis I continues in one or several oocytes each month but halts again at metaphase II Meiosis is only completed if the ovum is fertilized

Oogenesis A diploid oogonium divides by mitosis to produce a stem cell and another cell that specializes into a primary oocyte In meiosis I, the primary oocyte divides

40 Oogenesis A diploid oogonium divides by mitosis to produce a stem cell and another cell that specializes into a primary oocyte In meiosis I, the primary oocyte divides unequally forming a small polar body and a large secondary oocyte In meiosis II, the secondary oocyte divides to form another polar body and a mature haploid ovum

41 Oogenesis

Asexual vs. Sexual. Biology 3201 Unit II Reproduction How Reproductive Cells are Produced. two parents offspring is unique

Asexual vs. Sexual. Biology 3201 Unit II Reproduction How Reproductive Cells are Produced. two parents offspring is unique Biology 3201 Unit II Reproduction 14.2 How Reproductive Cells are Produced Asexual vs single parent offspring identical to parent parent passes on ALL its genes results in a clone Sexual two parents offspring