1. Cell Division Mitosis and Meiosis

2. Types of Cell Division Mitosis
occurs in all body cells (somatic cells) in animals, plants, and humans
production of 2 identical daughter cells that are diploid
growth or replacement of body cells.
asexual reproduction. (offspring and parents are identical)

3. Types of Cell Division 2) Meiosis
 occurs only is sex cells (sperm and egg)
production of the 4 non-identical gametes (sex cells) that are haploid
Sperm and eggs have half the genetic information
sexual reproduction

5. The Cell Cycle 10% time dividing (mitotic phase/meiotic phase)
90% time interphase (G1, S, G2 phases)

6. Interphase
1) G1 (gap phase) -manufactures proteins and amino acids needed for both cell processes and cell division, carries out metabolic duties
Cell grows
2) S phase (synthesis phase) – DNA replicates.
-longest stage of the cell cycle

7. 3) G2 (gap phase) grows larger
increases the rate of protein synthesis and prepares to divide.
grows larger

8. Division Mitosis or Meiosis
cell can divide only about 50 times on average.
To ensure that the cells in a tissue are healthy, cells will undergo a form of cell suicide called apoptosis.
Cell Death

9. Terms
Chromatin – complex long threads made of DNA and protein that makes up chromosomes
Uncondensed chromosome – long, thin strands not visible with light microscope
Condensed chromosome – short and visible

11. Chromosome vs. Chromatid
Chromosomes replicate before division to form 2 matched sister chromatids

12. Ploidy Humans have 46 chromosomes (diploid or 2N)
Sex gametes have 23 chromosomes (haploid or N
Some organisms have polyploidy
Ex) corn – 4n (tetraploidy)

13. Homologous chromosomes
–same size and shape and carry the genes for the same traits, but have different details
Humans have 23 homologous chromosomes for a total of 46

14. Gene basic unit of heredity sequence of nucleotide bases in DNA.
codes for a specific proteins

15. Autosomes – chromosomes that do not influence gender (humans have 22 pairs of these)
Sex Chromosomes – X and Y chromosomes that determine gender in humans (humans have 1 pair of these, the 23rd chromosome pair)

16. Mitosis

17. Prophase (longest phase)
Early: chromatin condenses to form chromosomes, centrioles move to poles and attach to spindle fibres
Late: spindle fibres attach to centromere, nuclear membrane dissolves

18. Metaphase
chromosomes line up on the equatorial plate (center of the nucleus)

19. Anaphase
Spindle fibres contract from the centrioles and sister chromatids begin to separate apart, immediately chromosomes being to unravel

20. Telophase
nucleolus re-appears, nuclear membrane reforms, the chromosomes unravel to form a loose mass of chromatin
cells undergo cytokinesis (divide cytoplasm)

21. Plant vs Animal Cells
a cell plate forms between the new daughter cells
the cell membrane pinches in between the two daughter cells

22. Mitosis Overall

23. Some Methods of Asexual Reproduction
1.  Binary fission - equal division of both the organism cytoplasm and nucleus to form two identical organisms
ex: Protist, amoeba 

24. 2) Budding - one parent dividing its nucleus (genetic material) equally, but cytoplasm unequally ex: Fungi-  yeast

25. Meiosis – Sexual Cell Division
Occurs in sexual reproduction
The end result is 4 gamates that are genetically different
Spermatagonium4 sperms
Oogonium 4 eggs

26. Meiosis I – Reduction Division
Prophase I – homologous chromosomes undergo synapsis (pair up) and crossing over occurs.
-also, as in mitosis prophase:
Chromos condense
Nuclear membrane disappears
Centrioles move to opposite
poles
-tetrad

27. Metaphase I – homologous pairs line up along the equatorial plate, spindles insert into the centromeres.

28. Anaphase I – homologous chromosomes separate and are pulled to opposite poles
= segregation

29. Chromosomes undergo independent assortment in during Anaphase I
-increases genetic diversity

30. Telophase I – daughter cells separate, each has one chromosome from each homologous pair.
-reduction has occurred so that the new cells will be haploid (n)
-cytokinesis occurs

31. Meiosis II – like mitosis but no initial replication of DNA -very brief, not as long as meiosis I
Prophase II –spindles form

32. Metaphase II –chromosomes align at the equatorial plate

33. Anaphase II – the daughter chromatids separate and move towards separate poles

34. Telophase II – spindle fibres disappear, nuclei reform and cytokinesis takes place. (All 4 daughter cells are haploid.)

35. How many genetic combinations of gamates?
The number of possible chromosome combination in a gamate is 2^n
Where ‘n’ is the haploid number
Ex. Humans n=23, thus 2^23 =8, 388, 608 different combinations!!
Now THAT’S diversity!!

36. NOVA Online | 18 Ways to Make a Baby | How Cells Divide: Mitosis vs
NOVA Online | 18 Ways to Make a Baby | How Cells Divide: Mitosis vs. Meiosis (Flash)

37. Human Life Cycle

38. Fern Life Cycle

39. Oogenesis

40. Spermatogenesis

41. Oogenesis vs Spermatogenesis
Oogenesis (female)
meiosis II completes only if egg is fertilized
Secondary oocyte receives most of the cytoplasm and becomes the egg
polar bodies have less cytoplasm and degenerate
one egg cell is produced
Spermatogenesis (male)
meiosis I and II are both completed before fertilization
each sperm cell produced receives an equal share of cytoplasm
flagellum forms from one of the centrioles
four spermatids are produced

42. Human Karyotype Chart

43. Gender
Female is XX
Male is XY
XX XY

44. Chromosomal abnormalities can be detected by doing a karyotype chart.
Fetal cells are collected through amniocentesis or chorionic villi sampling

45. Successful cell division relies on 2 things:
1. accurate replication of the chromosomes
2. exact separation / distribution of the chromosomes

46. Trisomy –three chromosomes replace a normal pair (47 chromosomes in humans)

47. Abnormal Meiosis
Non-disjunction – occurs during meiosis when two homologous chromosomes move to the same pole. Chromosomes do not separate properly
Normal Division Non-disjunction

48. Some Common Genetic Disorders
Down’s syndrome – trisomy 21
Extra 21 chromosome
more common in children born to women over 40
characterized by short stature, folds to the eyelids, stubby fingers, wide gap between 1st and 3rd toes, large fissured tongue, round head, palm creases, mild to severe mental retardation.

50. Edward’s syndrome – trisomy 18
results in severe overall defects with a life expectance of only 10 weeks
Patau’s syndrome – trisomy 13
results in non-functioning eyes, severe deficits and limited life expectancy.

51. Klinefelter’s syndrome – XXY male
sterile males with underdeveloped testes, overdeveloped breast tissue and sub-normal intelligence

52. Metafemale – XXX female
no obvious deficits however menstrual irregularities and early menopause are common, some have increase aggression
XYY male
taller than normal, recurrent acne

53. Monosomy –one chromosome replaces a normal pair (45 chromosomes in humans)

54. Turner’s syndrome – XO female
females with short stature, broad chest, heart defects, lack of breasts and absence of sexual maturation and menstruation
Cri du Chat syndrome
deletion of a portion of one copy of chromosome number 5, malformed face and head, short life

55. Societal Issues of Cell Division
Cloning
identical offspring are formed from a single cell or tissue of the parent. (similar to mitosis)
when plants send out runners, when bacteria divide and in identical twins.

57. How to Clone: (the quick and easy, yet not so successful way)
Take an egg cell from an adult female and remove the nucleus (enucleation).
Replace the nucleus with the nucleus from a body cell of the individual to be cloned.
(the cell must be toti-potent, or have its identity genes turned off) (you can use stem cells here)

58. Zap it!!! (a little magic is required here)
Implant the zygote or blastula into the mother’s uterus.
Wait until the gestational period is up and voila!
Click and Clone

60. Dolly
nucleus from udder cell put into egg cell

61. Problems with cloning:
some think it is wrong!!! (ethical issue)
artificially cloned organisms seem to age faster
it is very time and resource consuming and is not guaranteed to work

62. Cell Ageing
the ends of the chromosomes, called telomeres, shorten each time a cell divides, and when they become critically short, the cell dies.
Totipotent: when cells reach a certain number of divisions, or age, DNA begins to altered

63. Cancer May be caused due to mutation of genes
abnormal, uncontrolled cell division.
May be caused due to mutation of genes
Tumour suppressor genes – suppress cell division. (mutation turns these off)
Proto-oncogenes – stimulate cell division. (mutation turns these on)
Telomeres do not shrink in cancerous cells

64. Why is cancer bad
Cancer cells do not participate in helping the body to function.
Cancer cells require and take away nutrients
Cancer cells can break away (metastasis) from the tumour mass and spread to other parts of the body.
NOVA Online | Cancer Warrior | How Cancer Grows