Unit 5 – Cell Division

1. Unit 5 – Cell Division Warm Up: Pick up the new Unit 5 Packet and please put away cell phones

2. Day 1 • We will cover Mitosis and the Cell Cycle Today • Warm up video: https://www.youtube.com/watch?v=Q6ucKWIIFmg 15 minutes Station 1: Cell Growth & Division Notes (pages 1-7) with Mrs. Papaleo at her Table 15 minutes Station 2: Cell Cycle Coloring (pages 9-10) 15 minutes Station 3: Complete Foldables that were started after the Cell Test, optional SOL practice questions if you don’t want to participate 15 minutes Station 4: Mitosis Stages drawing (page 11) Review Video if Time, first thing next time if not: https://www.youtube.com/watch?v=ofjyw7ARP1c • Homework: Page 13, Color and Label Mitosis Diagram

3. Cell Growth • Limits to Cell Growth/Size • DNA “Overload” – If a cell grows too large, its DNA could no longer serve the needs of the entire cell • Exchanging materials – if a cell is too large, is struggles to move enough nutrients & wastes throughout the cell and to the cell membrane

4. Surface Area to Volume Ratio • Surface Area = length x width x # of sides • Volume = length x width x height • Surface Area to Volume Ratio = SA/V • Volume increases more rapidly than surface area, causing the ratio to decrease • 2 lane main street into a town will experience more traffic as town gets bigger, and it takes longer to get to center of town as size of town increases

5. Fill it in!

6. Why Do Cells Need to Divide and Reproduce? • Growth – new cells are needed to grow tissues and organs • Replacement & Renewal – old/damaged cells die & are replaced with new • Reproduction • unicellular organisms divide to make new organisms • multicellular organisms divide cells to make sex cells (gametes).

7. Chromosome Structure • Gene– DNA is a large molecule broken down into hereditary units called genes • DNA is organized & packaged into chromosomes during cell division • Chromosome – DNA wound or coiled tightly around proteins (histones) • Prokaryote Chromosome – a single, circular loop of DNA • Eukaryote Chromosome – many linear DNA molecules packaged into chromosomes

8. Cont’d • Structure – fully condensed, duplicated • A chromosome is made of 2 identical halves. Each half is called a chromatid. • A centromere holds 2 chromatids together to make a chromosome. • DNA is packaged as a chromosome only during cell division, after it has been copied. • When a cell is not dividing, its DNA is packaged more loosely as chromatin.

9. Chromosome #’s - each species has a different number of chromosomes Sex Chromosomes – and X or Y chromosome • They determine the sex of the individual • Female = XX Male = XY

10. Autosomes – all remaining chromosomes • In humans: 44 autosomes + 2 sex chromosomes = 46 total chromosomes • The 44 autosomes in a human are actually 22 pairs. An individual gets a copy of each chromosomes from each parent. Homologous Chromosomes – a pair of chromosomes • A human has 22 homologous chromosome pairs • A homologous pair are the same size, shape, and contain the same types of genes for the same traits. • Each chromosome can have different specific genes than its homologous pair

11. Diploid Cells • Are cells having all homologous pairs and 2 sex chromosomes • All cells except gametes (gametes = sex cells: egg and sperm cells) • Diploid cell are abbreviated as 2n, where n = # of 1 set of chromosomes. • Also called body cell, or somatic cells. • The chromosomes of diploid cells can be arranged and studied using karyotypes. Haploid Cells • Cells that contain only 1 chromosome from the pair of homologous chromosomes and 1 sex chromosome. • Haploid cells are abbreviated as n. • Haploid cells are gametes.

12. 2 sister chromatids join to make a chromosomethey are connected at the centromere

14. Chromosome # Example: A male human has 46 total chromosomes. (A chromosome is made of 2 chromatids, duplicated copies of the same DNA molecule) • # of autosomes = • # of sex chromosomes = • The sex chromosomes are • # of homologous pairs = • Diploid # (2n) = • Haploid # (n) =

15. Eukaryotic Cell Cycle • Cell Cycle – repeating events of growth and division during the life of a cell • Interphase – time when cell is not dividing • G1 Phase – cells grows rapidly as it makes more organelles • S Phase – DNA/chromosome is copied • G2 Phase – cell continues to grow and makes organelles for cell division • G0 Phase – when cell doesn’t divide (instead of G1, S, & G2 Phases)

16. Mitosis – division of the nucleus (DNA) Prophase– 1st step • DNA is packaged into chromosomes • Nucleolus and nuclear membrane break apart • Centrioles move to opposite ends of the cell Metaphase – 2nd step • Spindle fibers coming from the centrioles attach to the centromeres of the chromosomes • Chromosomes line up in the middle of the cell

17. Anaphase – 3rd step • Spindle fibers pull chromatids apart at the centromere • Each chromatid is now considered a chromosome! • Telophase – 4th (last) step • Spindle fibers disappear • Nuclear envelope reforms around each set of chromosomes

18. Cytokinesis • Begins during telophase. • Is the division of the cell/cytoplasm. • Animal cells: cell membrane pinches inward making a cleavage furrow. This continues until 2 cells are formed. • Plant Cells: a cell plate forms between the 2 sets of chromosomes. Mitosis happens in somatic cells and makes 2 diploid cells

19. Mitosis In a Plant Cell

20. Mitosis in an animal cell

21. In Summary – the cell cycle

22. In Summary - Mitosis

23. What will effect cell Division? Controls on Cell Division • Physical contact • Cells tend to divide until a space has been filled. • Once that space has been filled, or the cells contact each other, they stop dividing. Cell Cycle Regulators • Cyclin – protein that regulates the cell cycle • High levels of cyclin = cell division • Low levels of cyclin = Interphase

24. Uncontrolled Cell Growth • Cancer – cells lose the ability to control cell divison/growth • Cancer cells do not respond to the signals that regulate the growth of most other cells. • As a result, they form masses of cells, tumors, that can damage the surrounding tissues.

25. Review Video https://www.youtube.com/watch?v=ofjyw7ARP1c

26. Day 2 – Mitosis and Cell Cycle Review • Let’s go over the notes on the board with the powerpoint now that your notes are filled in from last class • And in class with a partner we will complete the Cell Division Gizmo to practice! • Quiz Next Class!

27. Day 3- Mitosis Lab and Mitosis Quiz • Compare the stages on Mitosis on slides under the microscope, to practice before Quiz • Pages 1-14 should be complete in your packet • Homework: vocabulary on page 22 & page 24

28. Day 4- Meiosis • Meiosis Notes on pages 14 & 15 • Video to see Meiosis in action • Compare Mitosis and Meiosis on pages 16-19 in packet • Venn Diagram and Vocabulary on pages 23 and 25 • Study for Quiz for homework and complete pages 20-21 so packet is done!

29. Meiosis Notes • Meiosis – cell division that halves the number of chromosomes in new cells, making haploid cells • *Recall, haploid cells in human are egg/sperm cells, called gametes, and contain 23 chromosomes.

30. Stages of Meiosis Interphase • cells go through G1, S, and G2 phases; • DNA is copied and cells grow larger.

31. Meiosis I Prophase I • DNA is coiled into chromosomes & nucleus breaks down • Centrioles move to ends of cell; spindle fibers appear • Chromosomes pair up (in homologous pairs) and twist together. • Portions of a chromatid can break off and reattach to the identical chromatid on its homologous chromosome = crossing over

32. Prophase 1 and Crossing Over

33. Metaphase I • Homologous chromosomes line up randomly in the center of the cell • Spindle fibers attach to the centromeres

34. Anaphase I • Spindle fibers pull homologous chromosomes apart. • The direction the chromosomes are pulled is random = independent assortment

35. Telophase I • Chromosomes move to opposite ends of the cell • Cytokinesis occurs Meiosis I results in 2 new haploid cells

36. Meiosis II • Begins immediately after Meiosis I. • Both cells from Meiosis I go through Meiosis II. • DNA is not copied this time!!!!!!!

37. Prophase II – spindle fibers reform, centrioles move to opposite ends of cell • Metaphase II – single chromosomes line up in the middle of the cell • Anaphase II – spindle fibers attach at centromeres and pull chromatids apart • Telophase II – chromatids move to opposite ends, and nucleus forms around them and cytokinesis occurs Meiosis II results in 4 new Haploid cells

38. Meiosis

39. Meiosis Forms Gametes • The 4 haploid cells produced in Meiosis are gametes (sex cells = egg/sperm) • Spermatogenesis – production of sperm cells • Oogenesis – production of mature egg cells or ova (singular = ovum) Genetic Variation in Meiosis • Crossing Over – switching of DNA between chromatids of homologous pairs; occurs during prophase I • Independent Assortment – each homologous pair is separated independent of how the other pairs are separated. • Random Fertilization – of the 4 gametes produced in meiosis, any one can fertilize (join) with another gamete

40. Can you compare them?