1. Meiosis

2. Called Somatic Cells Mitosis is 99.9% of your body’s cells.
(Diploid 46 chromosoms)
Copyright © 2010 Ryan P. Murphy

3. Gametes (Haploid) 23 Chromosomes
Mitosis is 99.9% of your body’s cells.
Meiosis occurs in your sex cells.
Gametes (Haploid)
23 Chromosomes
Copyright © 2010 Ryan P. Murphy

4. Only two types of cells in your body are haploid
Only two types of cells in your body are haploid. Two haploids make a diploid.
Sperm
Eggs

6. Haploid or Diploid?
Egg Cell
Nerve Cell
Skin Cell
Sperm Cell
Stem Cell

7. Fertilization: The joining of the egg and the sperm.
The sperm and egg each contain ½ genetic info needed to make a diploid cell…YOU!
Sex cells are also called gametes
Copyright © 2010 Ryan P. Murphy

8. Sex Cells example/
If sex cells each had the total 46 chromosomes (2 complete sets), when they combined, there would be 92 chromosomes. If a cell with 92 combined with another cell of 92, there would be 184…this is problematic.

13. Reduction Division
Sex cells are reduced from the diploid to ½ of the normal number (or a HAPLOID condition)
In humans, 46 chromosomes must be reduced to 23
This is the number of chromosomes found only in egg and sperm cells (gametes)

14. Meiotic Process
Reproductive cells are reduced by the process of Meiosis

15. Mitosis Mitosis 23 23 46 46 Egg Fertilization
Sexual Reproduction: Both parents provide half of the genetic information. 46 46
Sex cell formation
Meiosis
Egg 23
Sperm 23
Nine months later…
Fertilization
Mitosis
Mitosis

16. Homologous Pairing
Homologous pairs- Chromosomes are always paired with a matching set. These are separated in Meiosis I
An organism receives ½ of its chromosomes from each parent (making 1 full set)

19. Phases of Meiosis
Meiosis is a two part process that is nearly identical to mitosis
Meiosis I
Prophase I – replicated pairs of chromosomes thicken and condense
Metaphase I – Chromosomes line up on cell plate
Anaphase I – Homologous pairs are pulled apart by spindle fibers
Telophase I – Cytokinesis takes place

21. Meiosis II Prophase II – sister chromatids (chromosome) condense
Metaphase II – sister chromatids (chromosome) center on cell plate again
Anaphase II – Sister chromatids are pulled apart by spindle fibers
Haploid Cells – 4 haploid cells are produced through cytokinesis

23. A look at both Meiosis I & II

25. New Chromosomal Combinations
Meiosis allows for variation among organisms
DNA is different on each chromosome
Genetic make-up is unique to each individual
Variation is good
Helps organisms to more readily adapt to their surroundings and continue their survival

26. Reduction of genetic information
Produces four different reproductive cells
Copyright © 2010 Ryan P. Murphy

27. Reduction of genetic information
Produces four different reproductive cells
Copyright © 2010 Ryan P. Murphy

28. Reduction of genetic information
Produces four different reproductive cells
Copyright © 2010 Ryan P. Murphy

29. Reduction of genetic information
Produces four different reproductive cells
Copyright © 2010 Ryan P. Murphy

30. Reduction of genetic information
Produces four different reproductive cells
Copyright © 2010 Ryan P. Murphy

31. All Different Reduction of genetic information
Produces four different reproductive cells
All Different
Copyright © 2010 Ryan P. Murphy

32. Also called Homologous
Crossing Over : Genetic segments of information are swapped when the chromosomes are next to each other (random and creates millions of possibilities)
Also called Homologous
Recombination
Copyright © 2010 Ryan P. Murphy

33. Which sperm will fertilize the egg?
It’s usually only one.
A B C D
Copyright © 2010 Ryan P. Murphy

34. Answer. It’s completely random
Answer! It’s completely random. This is what makes you completely unique. C
Copyright © 2010 Ryan P. Murphy

35. Only one of the eggs will become a viable egg for fertilization.
A B C D
Copyright © 2010 Ryan P. Murphy

36. Only one of the eggs will become a viable egg for fertilization.
A B C D
Copyright © 2010 Ryan P. Murphy

37. Only one of the eggs will become a viable egg for fertilization.
Called Polar
Bodies
A B C D
Copyright © 2010 Ryan P. Murphy

38. Only one of the eggs will become a viable egg for fertilization.
They shrivel and die…
Called Polar
Bodies
A B C D
Copyright © 2010 Ryan P. Murphy

39. Only one of the eggs will become a viable egg for fertilization.
They shrivel and die…
Called Polar
Bodies
A B C D
Copyright © 2010 Ryan P. Murphy

40. Karyotype
An ordered, visual representation of the chromosomes in a cell
Chromosomes are photographed when they are highly condensed, then photos of the individual chromosomes are arranged in order of decreasing size:
In humans each somatic cell has 46 chromosomes, made up of two sets, one set of chromosomes comes from each parent
5 µm
Pair of homologous
chromosomes
Centromere
Sister
chromatids

42. Autosomes = Chromosome pairs 1-22 look alike and code for body
Sex Chromosomes=
The 23rd pair determines
the sex of the individual
(XX=female, XY=male)

43. Chromosome types Non-homologous chromosomes Look different
Control different traits
Sex chromosomes
Are distinct from each other in their characteristics
Are represented as X and Y
Determine the sex of the individual, XX being female, XY being male (in mammals)
In a diploid cell, the chromosomes occur in pairs. The 2 members of each pair are called homologous chromosomes or homologues.

44. Chromosomes A diploid cell has two sets of each of its chromosomes
A human has 46 chromosomes (2n = 46)
In a cell in which DNA synthesis has occurred all the chromosomes are duplicated and thus each consists of two identical sister chromatids
Maternal set of
chromosomes (n = 3)
Paternal set of
2n = 6
Two sister chromatids
of one replicated
chromosome
Two nonsister
chromatids in
a homologous pair
Pair of homologous
chromosomes
(one from each set)
Centromere

45. Chromosomal Abnormalities
Nondisjunction
Failure of chromosomes to separate during cell division
Can cause cell death but usually does not harm the organism
When nondisjunction occurs when making sperm and eggs the organisms is affected.
One sperm/egg may receive an extra chromosome while another would receive one less than it should have

46. Nondisjunction cont. In a sperm or egg cell… Trisomy or Monosomy
Monosomy – one too few chromosomes
Most often causes death
(XO) is an exception (Turner’s Syndrome)
Trisomy: one too many chromosomes
Trisomy 21 (Down’s Syndrome)

48. Klinefelter’s Syndrome XXY

50. Trisomy 18, Edward’s Syndrome

51. Trisomy 13 – Patau Syndrome

53. Chromosomal mutations
Deletion – piece of the chromosome is lost
Duplication – piece of DNA is copied too many times in one chromosome
Inversion – segment flips within chromosome
Translocation – segment breaks off and joins another chromosome

54. Deletion of part of the 5th Chromosome
Resulting in Cri-Du-Chat Syndrome (Cat Cry Syndrome)

55. Duplications of Various Chromosomes:
Pallister-Killian Syndrome
Weak muscle tone. 30% able to walk without assistance

56. Inversion

57. Inversion
Angleman’s Syndrome- developmental and intellectual retardation with frequent seizures

58. Translocation Sometimes it is even breaking, sometimes it is uneven.
Different effects on different chromosomes

59. Translocation between 13 & 14
Cancer, Infertility and Down’s Syndrome are common expressions of Translocations – though most are normal.

60. Nondisjunction Cont. Sometimes ALL OF YOUR CHROMOSOMES can be doubled!
In animals this is rare and results in death
In plants, this will often produce hardier & healthier specimens
Potatoes, oats, bananas, peanuts, barley, plums, wheat, apples, sugar cane, coffee & cotton are such examples