1. Bellringer Mon, 12/7 1.Mitosis=cell reproduction in which two cell are made from one cell (Asexual reproduction) 2. Meiosis =cell reproduction that forms eggs and sperm (sexual reproduction) REMINDERS: Progress Reports Grades this Wed,LAB FEE anytime!!!

2. Reminders, Review and Something New Chromosomes = condensed chromatin (DNA), 46 in Humans, 23 pairsChromosomes = condensed chromatin (DNA), 46 in Humans, 23 pairs Genes- sections of a chromosome responsible for one trait (eye color, height, etc)Genes- sections of a chromosome responsible for one trait (eye color, height, etc)

3. Remembering Meiosis Mitosis is a process that occurs in almost every cell of your body (body cells), except the sex cells, or gametes. Mitosis = My toe sis, it happens in your toes! Meiosis is a process of cell division that doesn’t happen in your toes, it only happens in your sex cells, gametes Meiosis = My OH! Sis (as in uh-oh!) Box 40 Box 51 Box 52

4. Cancer Cancer cells do not respond to the signals that regulate growth of most cells. They divide uncontrollably and form masses of cells called Tumors that can damage the surrounding tissues. Untreated Breast Cancer Tumor on the eye Box 35 Box 36 Tumors = masses of uncontrollably dividing cells Box 43 Box 44

6. How many chromosomes do we have? 23-Mother + 23-Father = Total 46 Chromosomes 1 to 22- autosomes Chromosome #23- sex chromosome

9. What is MEIOSIS? A type of cell division that results in 4 daughter cells with half as many chromosomes as the parent cells!

10. Gamete Formation Why do we even have Meiosis? To make gametes (eggs and sperm). Male gametes = sperm Female gametes = eggs Why do we need eggs and sperm? Skip Box 59 Box 71 For Sexual Reproduction, where egg and sperm unite to make an embryo Box 72

11. Meiosis Parent cell – chromosome pair Chromosomes copied 1 st division - pairs split 2 nd division – produces 4 gamete cells with ½ the original no. of chromosomes

12. only gametes or sex cells gametes: males-sperm and females-eggs What cells go through meiosis?

13. Why 1/2 the chromosomes in gametes? the male and female gametes need to provide ½ the chromosomes each – so the offspring has 1/2 the genes from the mother and 1/2 the father!the male and female gametes need to provide ½ the chromosomes each – so the offspring has 1/2 the genes from the mother and 1/2 the father!

14. Rules of Meiosis 1.Chromosomes are found in homologous pairs. 2. Chromosomes carry genes. 3. Genes are parts of a chromosome responsible for a trait: eye color, height, hair type, etc.

15. What are Homologous chromosomes? Paired chromosomes with genes for the same traits arranged in the same order

16. Again, how many chromosomes do we have? 23 (Maternal) + 23 (Paternal)= Total 46

17. Gametes (sex cells)- haploid n = number of chromosomes from each parent n Body cells diploid 2n

18. Diploid vs. Haploid OrganismGamete (n)Body Cell (2n) Humans2346 Mosquito36 Toad1122 Potato2448 Dog3978

19. Stages of Meiosis Meiosis I and Meiosis II

21. Meiosis I Prophase I: homologous pairs, pair up. Crossing over occurs! Metaphase I: chromosomes meet at the middle of the cell

22. Anaphase I: homologous chromosomes (each with 2 chromatids) move to opposite ends Telophase I: 2 nuclei form, original cell divides

23. Meiosis II No INTERPHASE or DNA copied between I and II Prophase II: chromosomes come together again and start to move toward the equator Metaphase II chromosomes line up in the middle

24. Anaphase II: chromatids separate to opposite poles Telophase II: two nuclei form - and cells divide

25. Meiosis – PMAT I and II Parent cell 4 gametes 1 st division 2 nd division

26. Results after meiosis… 4 Sex cells (gametes) that are haploid (n) - half as many chromosomes as parent cell (2n)

27. In females = one large egg cell and 3 polar bodies

28. In males meiosis results in 4 sex cells * FYI: meiosis produces roughly 250,000,000 sperm per day all their adult life

29. Fertilization Egg (n) + Sperm (n) = Zygote (2n)

30. A fertilized egg with diploid set of chromosomes. After fertilization, the zygote divides by mitosis and becomes an embryo. Later, the embryo becomes a fetus Zygote>Embryo>Fetus

31. 2 Key Differences Between Mitosis and Meiosis 1. Look at the Way Chromosomes Pair and Align Mitosis The first (and distinguishing) division of meiosis

32. 2. Crossing-Over Chromosomes exchange genetic material between homologous pairs!

34. Meiosis error - fertilization Should the gamete with the chromosome pair be fertilized then the offspring will not be ‘normal’. In humans this often occurs with the 21 st pair – producing a child with Downs Syndrome

35. Meiosis – division error Chromosome pair

36. 21 trisomy – Downs Syndrome Can you see the extra 21 st chromosome? Is this person male or female?

37. Boy or Girl? The Y Chromosome “Decides” X chromosome Y chromosome

39. Boy or Girl? The Y Chromosome “Decides”

40. Watch and Listen for the difference between Meiosis and Mitosis!! http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf:: 535::535::/sites/dl/free/0072437316/120074 /bio17.swf::Comparison+of+Meiosis+and+ Mitosishttp://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf:: 535::535::/sites/dl/free/0072437316/120074 /bio17.swf::Comparison+of+Meiosis+and+ Mitosis