Cell Division and Reproduction

1. Cell Division and Reproduction

2. Cells divide for growth and repair (heal wounds and injuries).

3. The purpose of reproduction is to maintain a species. • There are two types of reproduction, asexual and sexual

4. 1. asexual reproduction • 1 parent involved so no sex is involved • Offspring will be genetically identical to the parent (clones of the parent) • Asexual reproduction the cells divide by mitosis

5. Diploid Cells become Diploid Cells • Diploid is the total chromosome number in any organism • Example- Human 46 chromosomes • All Body Cells or Somatic Cells (liver, skin, muscle) 2N 2N 2N

6. 6 types of Asexual Reproduction • 1. Binary Fission occurs in unicellular organisms. • Pinch into two equal parts • Examples: bacteria and amoeba

7. 2. Sporulation-reproductive cell is enclosed in a protective case called a spore • Examples-molds and mushrooms

8. 3. Parthenogenesis-the development of a male from and unfertilized egg • Examples-insects like bees, ant, termites, and fleas

9. 4. Budding- a small piece of the adult pinches off to form a new organism • Examples- yeasts and hydras

10. 5. Regeneration- regenerate lost body parts • Examples-starfish, earthworms, lizards

11. 6. Vegetative Propagation-(plants) Parent plant sends out a runner with a baby plant attached to it

12. The Cell Cycle

13. Interphase- The cell spends the majority of its life in interphase • G1 is the growth phase • S is the synthesis stage when the DNA in the nucleus is replicated getting ready for cell division

14. Each strand is a sister chromatid and they are held together by a centromere G2 is when organelles and lipids are produced to be ready for the cell to replicate

15. Interphasecentrioles are only presentin animal cells

16. Mitosis contains 4 steps- PMAT • 1. Prophase- The long stringy replicated DNA called chromatin in the cell condenses into chromosomes • Chromosomes consist of sister chromatids (one the original DNA strand and the other the newly replicated strand) hooked together by a centromere.

17. The nuclear envelope disintegrates • Nucleolus disappears • Spindle fibers that guide the chromosomes form from the centrioles in the animal cell and from the cell wall in the plant

18. Prophase

19. Metaphase • The chromosomes line up at the equator also called the metaphase plate.

20. Anaphase • The spindle fibers shorten breaking the centromere and pulling apart the daughter chromosomes

21. Telophase • Each side of the cell has a complete , identical set of chromosomes. • A nuclear envelope reforms around each complete set of chromosomes. • The chromosomes uncoil into chromatin. • The spindle fibers disappear. • Nucleolus reappears.

22. Cytokinesis-division of the cytoplasm, part of telophase

24. Summary of asexual reproduction • MITOSIS- PMAT • GENETICALLY IDENTICAL SET OF CHROMOSOMES • Somatic (body) cells • 1 division 2N 2N 2N

25. Cells will grow and divide in repair until they touch each other • Proteins control the timing of the cell cycle so it occurs in the correct order • Which cells in your body do you think undergo rapid mitosis?

26. Cancer is mitosis out of control due to external factors like tobacco and radiation or internal factors like the gene that stops the cell cycle • Stem cells are unspecialized early embryo cells that have the potential to differentiate into any type of cell.

27. Nerve cells (neurons), Heart cells (cardiac), Skeletal Muscle cells, can not undergo mitosis once fully developed • Stem cells could be the answer

28. 2. sexual reproduction • 2parents involved • Offspring will not be genetically identical to either parent because during fertilization the child receives DNA from the mother and father causing genetic variation

29. The gametes, sex cells, are made in the gonads (egg in the ovaries of the female and sperm in the testes in male) are created by meiosis with half the chromosome number. • Monoploid or Haploid-1N • After fertilization, the zygote has a complete set of chromosomes and grows by mitosis.

30. Fertilization in Human 22 X 22X 44 XX Girl XX 22 X 22 Y 44 XY Boy XY

31. Meiosis creates 1N cells-gametes in 2 divisions 2N 1N 1N 1N 1N 1N 1N

32. Interphase – same as mitosis with two growth phases and a synthesis phase where DNA is replicated • The first division is the reduction in chromosome number stage • Prophase 1- chromatin condenses forming chromosomes • homologous pairs (one from each parent) come together during synapsis forming a tetrad. • Homologous pairs are the same length, have the centromere in the same location, and have the same genes for the same traits on them

33. Homologous Chromosomes

34. Tetrads are formed when homologous chromosomes replicate prior to meiosis. Crossing over or exchange of genetic material occurs during synapsis increasing genetic variability.

35. Nuclear membrane disappears • Spindle fibers form and attach to tetrads Metaphase 1 Homologous pairs, tetrads, move to the equator

36. Anaphase 1- homologous chromosomes separate one moving toward each pole

37. Telophase 1- nuclear membrane reforms and cytokinesis creating 2 haploid daughter cells from a parent diploid cell There is no interphase Second division is like mitosis

38. Prophase 2- nuclear membrane disappears • spindle fibers form • centrioles to poles

39. Metaphase 2 –chromosomes line up at equator

40. Anaphase 2-spindle fibers pull sister chromatids apart at the centromere

41. Telophase 2- nuclear membrane reappears and cytokinesis forming 4 haploid cells

42. Gametogenesis

43. Mutations or changes in the chromosomes are passed from one generation to the next via the sex cells (egg and sperm) • Sexual Reproduction increases genetic variation

44. There are two types of sexual reproduction, external and internal. • 1. external sexual reproduction takes place outside the body (fish, amphibians) • Eggs and sperm are released into the environment • Many eggs and sperm are produced to increase the chance of fertilization • Usually occurs in an aquatic (water) environment because the eggs do not have a hard shell, they are gel

45. 2. Internal Fertilization occurs inside the body • The sperm is delivered close to the egg (reptiles, birds, and montremes) • Fewer eggs are produced because there is an increased chance of fertilization by many sperm • Usually occurs in land animals • Exceptions would be marine mammals and birds

46. Three Types of Mammals(have mammary glands, warm blooded, body hair, 4 chamber heart • 1. Montremes –Spiny Anteater and Duck-billed Platypus • Internal fertilization, External Development • Lay eggs • Babies Nurse

47. 2. Marsupials- Pouched Mammals, Kangaroos, Koala, Opossums • Internal fertilization and development • Get their nourishment from the yolk of the egg • Born underdeveloped and finish development in the mother’s pouch • Nurse on mother’s milk

48. 3. Placental Mammals- Human, Dog, Cat • Internal fertilization and development • Give birth to well-developed young that are nourished by the placenta in the uterus • Embryo is attached to the placenta by the umbilical cord.

49. Twins

50. Major structures • 1. Bladder- not part of the reproductive system but part of the excretory/urinary system • 2. Penis- Muscular organ that delivers sperm to the female • Erection is due to increased blood flow to the penis due to dilated blood vessels causing it to become hard and enlarged