1 Sexual Reproduction

2 Cellular Reproduction There are 2 types of reproduction: ■ Asexual Reproduction ■ Sexual Reproduction

3 Cellular Reproduction Asexual Reproduction (5 phases) ■ 1 mother cell divides into 2 daughter cells ■ Daughter cell is identical to its mother ■ Interphase + Mitosis ■ All human cells have 46 chromosomes called “DIPLOID cells” ■ Produce SOMATIC cells (not sexual cells)

4 Cellular Reproduction Sexual Reproduction (9 phases) ■ 1 mother cell divides into 4 daughter cells ■ Daughter cells have ½ the chromosomes of their mother (23) “HAPLOID cells ” ■ Interphase + Meiosis I + Meiosis II ■ Crossing over of genetic material often occurs. ■ SEXUAL cells (egg and sperm) known as “gametes”

Vocabulary

6 Gametes ~ Another name for eggs and sperm ~ They are haploid (In humans, that is 23 chromosomes) ~ They are sexual cells ~ They are produced by sexual reproduction

7 Vocabulary Sperm + egg = zygote

8 Homologous Chromosomes ■ A pair of chromosomes (maternal and paternal) that have similar/identical shapes and sizes. ■ Have genes for the same characteristics (ie: eye color). ■ Each locus (gene position) controls the same trait and is in the same place on homologous chromosomes.

9 Vocabulary Homologous Chromosomes chromatids tetrad

10 Homologous Chromosomes PaternalMaternal Eye color Hair color Locus

11 ■ There are 3 major steps: ~ Interphase ~ Meiosis I ~ Meiosis II Sexual Reproduction

12 Meiosis I (4 phases) ~ Prophase I ~ Metaphase I ~ Anaphase I ~ Telophase I

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14 Crossing Over ■ During Prophase I ■ One chromatid of each chromosome crosses over with the chromatid of the other chromosome. ■ The result is an exchange of their genetic material

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16 Meiosis II (4 phases) ~ Prophase II ~ Metaphase II ~ Anaphase II ~ Telophase II

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18 Meiosis II Interphase II – does not exist ** Don’t forget!! This process is now occurring in both daughter cells created during Meiosis I **

19 Attention!!!!!!!!!!!!! ■ Female meiosis is somewhat different. 4 gametes are initially created, but Cytokenisis is UNEQUAL. In this case, ONE GAMETE survives, and the other 3 are not viable.

20 Extra Notes

21 Interphase ■ Same as Interphase in Mitosis ■ Chromosome replication, growth and preparation (chromatin rolls etc) ■ Each of the replicated chromosomes possesses 2 chromatids which are attached at their centromere.

22 Prophase I ■ 2 homologous chromosomes combine. This combination is called a TETRAD ■ Spindle fibers grow, and attach to each side of the tetrad ■ The nuclear membrane and the nucleolus both disappear

23 Metaphase I ■ Spindle fibers pull on the tetrads, and align them in the centre of the cell.

24 Anaphase I ■ The tetrads separate and homologous chromosomes travel to the poles. ■ Homologous chromosomes are still attached by their centromeres.

25 Telophase I/Cytokinesis ■ Each pole has a diploid number of chromosomes. ■ Cytokinesis - 2 diploids cells are formed. ■ Spindle fibers and centrioles disappear. ■ The nuclear membrane sometimes reforms, and the nucleolus does not reform at this point.

26 Prophase II ■ Same as Prophase in Mitosis

27 Metaphase II ■ Same as Metaphase in Mitosis

28 Anaphase II ■ Same as Anaphase in Mitosis ■ DON’T FORGET! Chromosomes are separated into chromatids.

29 Telophase II/Cytokenisis ■ Same as Telophase in Mitosis EXCEPT with a haploid number of chromosomes ■ The nucleolus and nuclear membrane reform ■ Cytokinesis Important: 4 haploid gametes are formed.

30 Telophase II/Cytokinesis