Cell Division: A Complex Series of Changes in the Nucleus

1. Unit 6 Cell Division Reproduction and Development

2. Cell Division • A complex series of changes in the nucleus of a cell that leads to the production of two new cells. • The new cells are called daughter cells.

4. Why do cell divide?? • DNA overload- The cell’s DNA would no longer be able to serve the increasing needs of the growing cell. • Exchange of Materials -If cells grow to large, its more difficult to get rid of waste and take in nutrients.

6. Why do cells divide? • Growth- Humans start off as one cell by the time they are adults they have over 10 trillion cells. • Repair- tissue damage • Reproduction – Asexual or Sexual

7. What is inside of the Nucleus? • Genetic information that is passed on from one generation of cells to the next. • Chromosomes are made up of DNA which carries that genetic information • Chromosomes only visible during cell division

8. Chromosomes

9. Parts of the chromosome • Centromere - the part of a chromosome that links sister chromatids • Chromatid - one copy of a duplicated chromosome, which is generally joined to the other copy by a single centromere.

10. Homologous Chromosomes • Pair of chromosomes (maternal and paternal) that are similar in shape and size. • Homologous pairs (tetrads) carry genes controlling the same inherited traits. • Each locus(position of a gene) is in the same position on homologues. • Humans have 23 pairs of homologous chromosomes. 22 pairs of autosomes 1 pair of sex chromosomes

11. eye color locus eye color locus hair color locus hair color locus Paternal Maternal Homologous Chromosomes(because a homologous pair consists of 4 chromatids it is called a “Tetrad”)

12. “Sex Chromosomes” …….the 23rd set This person has 2 “X” chromosomes… and is a female. 23

13. Cell Cycle • Hormones send signals to cells to prepare for division when it is needed.

14. How do Cells divide? • Two Stages to a Cell Dividing • INTERPHASE – growth and preparation • CELL DIVISION - involves a complex series of changes in the nuclei of body cells that produce identical daughter cells • Mitosis • Cytokinesis

15. Mitosis • Prophase – Nuclear Membrane becomes invisible and chromosomes condense • Metaphase – Chromosomes line up in the middle • Anaphase – Chromosomes are pulled apart by spindle fibers that attach at the centromere • Telophase – Cell membrane pinches in and cytokinesis occurs (Cell plate forms in plant cell only)

16. Cytokinesis • Dividing of the Cytoplasm and the creation of two daughter cells.

17. Stages of Mitosis

18. Mitosis in Plants Same as mitosis in animals except: • Plants have no centrioles – spindle fibers take their place • Cell wall does not pinch because it is too rigid • Cell plate divides the cell into two

20. The Cell Cycle and Cancer

21. Cancer • Cells lose the ability to control growth • Uncontrolled growth of cells lead to tumors that can damage the surrounding tissue.

22. 1.Before a cell divides, the DNA is checked to make sure it has replicated correctly. (If DNA does not copy itself correctly, a gene mutation occurs.) There are several factors that regulate the cell cycle and assure a cell divides correctly. DNA replication Animation:click on DNA picture

23. 2. Chemical Signals tell a cell when to start and stop dividing. (Target cells animation: click on go sign)

24. 3. Neighboring cells communicate with dividing cells to regulate their growth also. (Normal contact inhibition animation: click on petri dish)

25. Tumors in Liver Tumor in Colon Cancer is a disease of the cell cycle. Some of the body’s cellsdivide uncontrollably and tumors form.

26. Mutations may be caused by: 1. radiation 2. smoking 3. Pollutants 4. chemicals 5. viruses Causes that disrupt the cell cycle.

27. While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.

28. Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors. Skin cancer (cancer cells dividing: click on picture.)

29. Normal Cell Division DNA is replicated properly. 2. Chemical signals start and stop the cell cycle. 3. Cells communicate with each other so they don’t become overcrowded. Cancer Cells Mutations occur in the DNA when it is replicated. 2. Chemical signals that start and stop the cell cycle are ignored. 3. Cells do not communicate with each other and tumors form. SUMMARY

30. Estimated Cancer Deaths in the US in 2013

31. Treating Cancers Cancer treatments include drugs that can stop cancer cells from dividing.

32. Mitosis and Asexual Reproduction

33. BACTERIA YEAST PLANTS Asexual Reproduction Occurs only through the process of mitosis • Each offspring has the same genetic information Where can asexual reproduction be found?

34. There are 5 different types of asexual reproduction. 1. Budding Parent divides unequally; new individuals develop from buds ex – yeast & hydra 2. Binary Fission Most simple form of asexual reproduction; Parent divides equally and results in two separate individuals Ex.-paramecium 3. Spore Formation Single specialized cells that germinate when released from parent. Usually covered by a protective coating for preservation.

35. 4. Regeneration/fragmentation Ability to regrow new body parts/ability to grow new Organism from parts. ex – hyrda, planaria, starfish, the bad guy from Terminator 2 5. Vegetative Reproduction/Propagation Refers to roots, stems, and leaves. Cells divide then differentiate to produce the same organism Ex.- strawberry plant, pick-a-back plant

36. MEIOSIS

37. Organisms that reproduce Sexually are made up of two different types of cells. • Somatic Cells are “body” cells and contain the normal number of chromosomes ….called the “Diploid” number (the symbol is 2n). Examples would be … skin cells, brain cells, etc. (Mitosis Cell Division) • Gametesare the “sex” cells and contain only ½ the normal number of chromosomes…. called the “Haploid” number (the symbol is n)….. Sperm cells and ova are gametes. (Meiosis Cell Division)

38. Meiosis Cell Division • Formation of sex cells (gamates) • Egg cell and Sperm cell (gamates) • 4 daughter cells are made with each having half the number of chromosomes as parent cell (n) Haploid • Reduction of chromosomes • Cells are NOT identical to parent

39. Meiosisis the process by which ”gametes” (sex cells) , withhalfthe number ofchromosomes,are produced. During Meiosis diploid cells are reduced to haploid cells Diploid (2n)  Haploid (n) If Meiosis did not occur the chromosome number in each new generation would double…. The offspring would die.

40. Stages of Meiosis

41. Tetrad nonsister chromatids Crossing Overcreates variation (diversity) in the offspring’s traits. variation

42. Question: • A cell containing 20 chromosomes(diploid)at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes?

43. Answer: • 10 chromosomes (haploid)

44. Sexual Reproduction

45. Sexual Development • Puberty is a period of rapid growth and sexual maturation during which the reproductive system becomes fully functional. • When puberty ends, reproductive organs are fully developed. • Puberty usually begins between the ages of 9 and 15, and usually starts one year earlier in females than in males.

46. Sexual Development • Puberty begins when the hypothalamus signals the pituitary to produce increased levels of two hormones that affect the gonads. • These hormones are follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

47. The Male Reproductive System • The Male Reproductive System • Release of FSH and LH stimulates cells in the testes to produce testosterone. • FSH and testosterone stimulate the development of sperm.

48. The Male Reproductive System Head Nucleus • A sperm cell consists of: • a head, which contains the nucleus • a midpiece, which contains energy-releasing mitochondria • a tail, which propels the cell forward Midpiece Mitochondria Tail

49. The Male Reproductive System • Male Reproductive System Urinary bladder Vas deferens Pubic bone Seminal vesicle Urethra Rectum Penis Prostate gland Epididymis Bulbourethral gland Testis Scrotum

50. The Female Reproductive System • Puberty in females starts when the hypothalamus signals the pituitary gland to release FSH and LH. • FSH stimulates cells within the ovaries to produce estrogen.