1. Mitosis vs. Meiosis

2. Chromosomes

4. Reflection
3/14 – Describe the chromosome disorder you have in your study. 3/16 – Contrast diploid and haploid cells.

5. Chromosomes Defined: Tightly coiled DNA Forms during cell division
New chromosomes created for new cells
2 Parts:
1) Chromatids: two identical parts of a chromosome
2) Centromere: Joins chromatids together
Chromosomes

6. KAROTYPE
Map of chromosome used to study disorders. You had a normal and abnormal set. How many chromosomes are normal?

8. Down Syndrome: What’s Wrong?
Writing notation:
1st: total chromosome #
2nd: Sex chromosomes
3rd: extra or missing
Down Syndrome: 47, XY, +21

9. Turner’s Syndrome: What’s Wrong?
Write the notation for Turner’s Syndrome.
45, X, -23 or
45, XO, -23

10. Patau’s Syndrome: What’s Wrong?
Write the notation for Patau’s Syndrome.
47, XY, +13

11. Klinefelter’s Syndrome: What’s Wrong?
Write the notation for Klinefelter’s Syndrome.
47, XXY, +23

12. Autosomes (The Autosomes code for most of the offspring’s traits)
In Humans the “Autosomes” are sets

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

14. In Humans the “Sex Chromosomes” are the 23rd set
Sex Chromosomes The Sex Chromosomes code for the sex of the offspring. ** If the offspring has two “X” chromosomes it will be a female. ** If the offspring has one “X” chromosome and one “Y” chromosome it will be a male.
In Humans the “Sex Chromosomes” are the 23rd set
XX chromosome - female
XY chromosome - male

15. Diploid Cells Diploid Cells = Cells with the full set of chromosomes
Paired chromosomes
Half of our chromosomes come from each parent (23 from each parent)
Somatic (non-sex) cells are diploid
Created by mitosis
Ex: Skin, Muscle, Nerve, Blood Cells

16. DIPLOID & HAPLOID HOMOLOGOUS CHROMOSOMES
Most cells have 2 copies of each chromosome = ______________
(one from mom; one from dad)
All BODY (___________) cells are diploid
DIPLOID 2n
HOMOLOGOUS CHROMOSOMES
= SOMATIC

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

18. Humans have 23 Sets of Homologous Chromosomes Each Homologous set is made up of 2 Homologues.

19. What is the human diploid chromosome number?
Remember…Diploid = total number of chromosomes Answer = 46

20. Haploid Cells
Haploid Cells = Cells with ½ the total number of chromosomes
Gametes (sex cells) are the only haploid cells
Ex: Sperm, Egg, Pollen
Chromosome number is reduced by meiosis
How do humans get 46 chromosomes?
Haploid sperm cell (23)
+ Haploid egg cell (23)
= Diploid zygote (46)

21. DIPLOID & HAPLOID
Some cells have only one copy of each chromosome = _____________
All sperm and egg cells
are haploid
HAPLOID 1n

22. Gametes
The Male Gamete is the Sperm and is produced in the male gonad the Testes.
The Female Gamete is the Ovum (ova = pl.) and is produced in the female gonad the Ovaries.

23. Karyotype Female Male Defined: Picture of an individuals chromosomes
Identify sex & chromosome defects
Size of final pair identifies sex
Same size: XX = female
Different size: XY = male
Normal human will have 46 chromosomes
Female
Male

24. Fertilization n=23 egg 2n=46 zygote
The fusion of a sperm and egg to form a zygote.
A zygote is a fertilized egg
n=23
egg
sperm
n=23
2n=46
zygote

25. Rat
Karyotype
What is the diploid chromosome number? 42

26. Rat
Karyotype
What is the haploid chromosome number? 21

27. Rat
Karyotype
How many chromosomes would be in somatic cells? 42

28. Rat
Karyotype
How many chromosomes would be in brain cells? 42

29. Rat
Karyotype
How many chromosomes would be in gamete cells? 21

30. Rat
Karyotype
How many chromosomes would be in egg cells? 21

31. Rat
Karyotype
How many chromosomes would be in muscle cells? 42

32. Rat
Karyotype
How many chromosomes would be in sperm cells? 21

33. Rat
Karyotype
Is this a male or female rat?
male

34. Quick Review Chromsomes are tightly coiled strands of DNA
Diploid (somatic) cells contain the entire set of chromosomes
Haploid (gametes) cells contain only ½ the total number of chromosomes

35. MEIOSIS 11-4 Making gametes…
Making gametes…

36. Interest Grabber
1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis? 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo? 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?
46 chromosomes
= 92; a developing embryo would not survive if it contained 92 chromosomes.
Sperm and egg should each have 23 chromosomes.

37. Remember from Chapter 1: CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS __________
REPRODUCE
Planaria animation: Family

38. Mitosis
Meiosis
Meiosis

39. ASEXUAL REPRODUCTION Bacteria reproduce using BINARY FISSION
Bacteria reproduce using
__________________________________
Budding & regeneration are used by plants and animals to reproduce asexually (mitosis)
BINARY FISSION
Planaria animation:

40. BINARY FISSION & MITOSIS
Produces cells that are __________ copies of parent cell
identical

41. ADVANTAGES OF ASEXUAL REPRODUCTION
Can make offspring faster
Don’t need a partner

42. DISVANTAGES OF ASEXUAL REPRODUCTION
ALL ALIKE
Species CAN’T change and adapt
One disease can wipe out whole population

43. SEXUAL REPRODUCTION DIFFERENT Combines genetic material
Family image from:
Combines genetic material
from 2 parents (sperm & egg)
so offspring are
genetically __________
from parents
DIFFERENT

44. ADVANTAGES OF SEXUAL REPRODUCTION
Allows for variation in population
Individuals can be different
Provides foundation for EVOLUTION
Allow species adapt to
changes in
their environment

45. + EGG SPERM  If egg and sperm had same number of
Image by Riedell
Image by Riedell
EGG +
SPERM 
If egg and sperm had same number of
chromosomes as other body cells . . .
baby would have too many chromosomes!

46. MEIOSIS is the way… to make cells with ½ the number of chromosomes
for sexual
reproduction

47. Click the image to play the video segment 11A.
Meiosis Overview
Click the image to play the video segment 11A.
Video 1

48. MITOSIS
Makes ___ cells genetically _________ to parent cell & to each other
Makes ___ cells
Makes __________
Used by organisms to: increase size of organism, repair injuries, replace worn out cells 2
identical 2n
SOMATIC (body)

49. MEIOSIS 4 1n Germ cells OR Gametes (sperm & eggs) sexual reproduction
Makes ____ cells genetically different from parent cell & from each other
Makes _____ cells
Makes ______________
Used for ____________ 1n
Germ cells
OR Gametes (sperm & eggs)
sexual reproduction

50. WHAT MAKES MEIOSIS DIFFERENT ?
SYNAPSIS & CROSSING OVER (PROPHASE I)
SEGREGATION &
INDEPENDENT ASSORTMENT (ANAPHASE I)
3. Skip INTERPHASE II (NO S)
CELL DIVIDES TWICE, BUT…
ONLY COPIES DNA ONCE

51. WHAT MAKES MEIOSIS DIFFERENT ?
Homologous chromosomes pair up during ________________
= ______________
PROPHASE I
SYNAPSIS
This group of FOUR (4)
chromatids is called a
_________________
TETRAD
Images modified from:

52. WHAT MAKES MEIOSIS DIFFERENT?
1. Exchange of DNA between homologous pairs = _____________ during PROPHASE I
CROSSING OVER
Allows shuffling of genetic material

53. Click the image to play the video segment. 11E
Crossing Over
SEE CROSSING OVER ANIMATION
Click the image to play the video segment. 11E
Video 5

54. HOMOLOGOUS CHROMOSOMES
SAME SIZE
SAME SHAPE
CARRY GENES for the SAME TRAITS
BUT ______________!
(Don’t have to have the SAME CHOICES)
Image modified by Riedell
NOT IDENTICAL

55. Allows for_________________ in different combinations
Image modified by Riedell
CROSSING OVER
rearranging of DNA
Allows for_________________
in different combinations
After crossing over, chromatid arms are________________ anymore
NOT IDENTICAL

56. WHAT MAKES MEIOSIS DIFFERENT ?
2.Separation during ANAPHASE I
SEGREGATION &
INDEPENDENT ASSORTMENT
Separates gene choices and allows shuffling of genetic material

57. Click the image to play the video segment 11D.
Segregation of Chromosomes
Click the image to play the video segment 11D.
Video 4

58. 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.
Gametes are 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.
n = number of chromosomes in the set… so….2n means 2 chromosomes in the set…. Polyploid cells have more than two chromosomes per set… example: 3n (3 chromosomes per set)

59. Sperm + Ovum (egg) Zygote
During Ovulation the ovum is released from the ovary and transported to an area where fertilization, the joining of the sperm and ovum, can occur…… fertilization, in Humans, occurs in the Fallopian tube. Fertilization results in the formation of the Zygote. (fertilized egg)
Sperm + Ovum (egg) Zygote
fertilization

60. Diploid (2n)  Haploid (n)
Meiosis is the process by which ”gametes” (sex cells) , with half the number of chromosomes, 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.

61. Meiosis Meiosis is Two cell divisions
(called meiosis I and meiosis II)
with only one duplication of chromosomes.

62. Meiosis in males is called spermatogenesis and produces sperm.
Meiosis in females is called oogenesis and produces ova.

63. 4 sperm cells are produced from each primary spermatocyte.
Spermatogenesis
n=23
sperm
haploid (n)
meiosis II
Secondary Spermatocyte
2n=46
human
sex cell
diploid (2n)
n=23
meiosis I
Primary Spermatocyte
Secondary Spermatocyte
4 sperm cells are produced from each primary spermatocyte.

64. Oogenesis
*** The polar bodies die… only one ovum (egg) is produced from each primary oocyte.

65. Interphase I Similar to mitosis interphase.
Chromosomes replicate (S phase).
Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres.
Centriole pairs also replicate.

66. Interphase I Nucleus and nucleolus visible. chromatin nuclear membrane
cell membrane
nucleolus

67. Meiosis I (four phases)
Cell division that reduces the chromosome number by one-half.
four phases:
a. prophase I
b. metaphase I
c. anaphase I
d. telophase I

68. Prophase I Longest and most complex phase.
90% of the meiotic process is spent in Prophase I
Chromosomes condense.
Synapsis occurs: homologous chromosomes come together to form a tetrad.
Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).

69. Prophase I - Synapsis
Homologous chromosomes
sister chromatids
Tetrad

70. During Prophase I “Crossing Over” occurs.
Crossing Over is one of the Two major occurrences of Meiosis
(The other is Non-disjunction)
During Crossing over segments of nonsister chromatids break and reattach to the other chromatid. The Chiasmata (chiasma) are the sites of crossing over.

71. Prophase I This is a crucial phase for mitosis.
During this phase each pair of chromatids don’t move to the equator alone, they match up with their homologous pair and fasten together (synapsis) in a group of four called a tetrad.
Extremely IMPORTANT!!! It is during this phase that crossing over can occur.
Crossing Over is the exchange of segments during synapsis.

72. Prophase I
centrioles
spindle fiber
aster
fibers

73. Crossing Over creates variation (diversity) in the offspring’s traits.
Tetrad
nonsister chromatids
chiasmata: site of crossing over
variation

74. Metaphase I Shortest phase Tetrads align on the metaphase plate.
INDEPENDENT ASSORTMENT OCCURS:
1. Orientation of homologous pair to poles is random.
2. Variation
3. Formula: 2n
Example: 2n = 4
then n = 2
thus 22 = 4 combinations

75. Metaphase I
The chromosomes line up at the equator attached by their centromeres to spindle fibers from centrioles.
Still in homologous pairs

76. Metaphase I
metaphase plate OR
metaphase plate

77. Anaphase I Homologous chromosomes separate and move towards the poles.
Sister chromatids remain attached at their centromeres.

78. Anaphase I
The spindle guides the movement of the chromosomes toward the poles
Sister chromatids remain attached
Move as a unit towards the same pole
The homologous chromosome moves toward the opposite pole
Contrasts mitosis – chromosomes appear as individuals instead of pairs (meiosis)

79. Anaphase I

80. Telophase I Each pole now has haploid set of chromosomes.
Cytokinesis occurs and two haploid daughter cells are formed.

81. Telophase I This is the end of the first meiotic cell division.
The cytoplasm divides, forming two new daughter cells.
Each of the newly formed cells has half the number of the parent cell’s chromosomes, but each chromosome is already replicated ready for the second meiotic cell division

82. Telophase I

83. Cytokinesis Occurs simultaneously with telophase I
Forms 2 daughter cells
Plant cells – cell plate
Animal cells – cleavage furrows
NO FURTHER REPLICATION OF GENETIC MATERIAL PRIOR TO THE SECOND DIVISION OF MEIOSIS

84. Meiosis II No interphase II (or very short - no more DNA replication)
Remember: Meiosis II is similar to mitosis

85. Meiosis II : Separates sister chromatids
Proceeds similar to mitosis
THERE IS NO INTERPHASE II !

86. Prophase II
Each of the daughter cells forms a spindle, and the double stranded chromosomes move toward the equator

87. Prophase II
same as prophase in mitosis

88. Metaphase II
The chromosomes are positioned on the metaphase plate in a mitosis-like fashion

89. Metaphase II
same as metaphase in mitosis
metaphase plate

90. Anaphase II
same as anaphase in mitosis
sister chromatids separate

91. Anaphase II The centromeres of sister chromatids finally separate
The sister chromatids of each pair move toward opposite poles
Now individual chromosomes

92. Telophase II Same as telophase in mitosis. Nuclei form.
Cytokinesis occurs.
Remember: four haploid daughter cells produced.
gametes = sperm or egg

93. Telophase II

94. Telophase II and Cytokinesis
Nuclei form at opposite poles of the cell and cytokinesis occurs
After completion of cytokinesis there are four daughter cells
All are haploid (n)

95. Non-disjunction
Non-disjunction is one of the Two major occurrences of Meiosis
(The other is Crossing Over)
Non-disjunction is the failure of homologous chromosomes, or sister chromatids, to separate during meiosis.
Non-disjunction results with the production of zygotes with abnormal chromosome numbers…… remember…. An abnormal chromosome number (abnormal amount of DNA) is damaging to the offspring.

96. Non-disjunctions usually occur in one of two fashions.
The first is called Monosomy, the second is called Trisomy. If an organism has Trisomy 18 it has three chromosomes in the 18th set, Trisomy 21…. Three chromosomes in the 21st set. If an organism has Monosomy 23 it has only one chromosome in the 23rd set.

97. Common Non-disjunction Disorders
Down’s Syndrome – Trisomy 21
Turner’s Syndrome – Monosomy 23 (X)
Kleinfelter’s Syndrome – Trisomy 23 (XXY)
Edward’s Syndrome – Trisomy 18

98. Amniocentesis
An Amniocentesis is a prrocedure a pregnant woman can have in order to detect some genetics disorders…..such as non-disjunction.

99. Amniocentesis
Amniotic fluid withdrawn

100. WHAT MAKES MEIOSIS DIFFERENT? What causes Variation!
1. CROSSING OVER (PROPHASE I)
2. INDEPENDENT ASSORTMENT (ANAPHASE I)

101. INDEPENDENT ASSORTMENT

102. Figure 13.7 The stages of meiotic cell division: Meiosis I

103. Figure 13.7 The stages of meiotic cell division: Meiosis II

104. One Way Meiosis Makes Lots of Different Sex Cells (Gametes) – Independent Assortment
Independent assortment produces 2n distinct gametes, where n = the number of unique chromosomes.
In humans, n = 23 and 223 = 6,000,0000.
That’s a lot of diversity by this mechanism alone.

106. Another Way Meiosis Makes Lots of Different Sex Cells – Crossing-Over
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.

107. Mitosis vs. Meiosis

108. The Key Difference Between Mitosis and Meiosis is the Way Chromosomes Uniquely Pair and Align in Meiosis
Mitosis
The first (and distinguishing) division of meiosis

109. Mitosis vs. Meiosis

110. Boy or Girl? The Y Chromosome “Decides”
X chromosome
Y chromosome

111. Boy or Girl? The Y Chromosome “Decides”

112. Meiosis – division error
Chromosome pair

113. Meiosis error - fertilization
Should the gamete with the chromosome pair be fertilized then the offspring will not be ‘normal’.
In humans this often occurs with the 21st pair – producing a child with Downs Syndrome

114. 21 trisomy – Downs Syndrome
Can you see the extra 21st chromosome?
Is this person male or female?

115. SEGREGATION (Anaphase I)

116. SEGREGATION & CROSSING OVER together make even more combinations
See an animation

117. INDEPENDENT ASSORTMENT

118. INDEPENDENT ASSORTMENT at ANAPHASE I
Lots of different combinations are possible!
This is why you don’t look exactly like your brothers and sisters even
though you share the same parents!

120. WHAT MAKES MEIOSIS DIFFERENT ?
Crossing over Segregation Independent assortment
are ALL ways MEIOSIS results in =______________________________
So daughter cells are ______________
from parents and from each other
GENETIC RECOMBINATION
different

121. WHAT MAKES MEIOSIS DIFFERENT ?
3. Skip INTERPHASE II (No S)
CELL DIVIDES TWICE, BUT …
ONLY COPIES ITS DNA ONCE
MITOSIS: G1 S G2 P M A T C       
MEIOSIS:
( I ) G1 A T C S G2 P M        P M A T C
( II )    

122. Click the image to play the video segment 11B. & C
Animal Cell Meiosis, Part 1 & Part 2
Click the image to play the video segment 11B. & C

123. Figure Meiosis
Section 11-4
Meiosis I

124. Figure Meiosis
Section 11-4
Meiosis I
Meiosis I

125. Figure Meiosis
Section 11-4
Meiosis I
Meiosis I

126. Figure Meiosis
Section 11-4
Meiosis I

127. Figure Meiosis
Section 11-4
Meiosis I

128. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

129. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

130. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

131. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

132. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

133. Ways Meiosis is different?
Homologous pairs match up & trade DNA (SYNAPSIS & CROSSING OVER) in PROPHASE I
SEGREGATION
& INDEPENDENT ASSORTMENT in Anaphase I
create genetic recombination
Skipping INTERPHASE II-
(Dividing TWICE but copying DNA once)
produces 1n cells