1. Meiosis and Sexual Reproduction

2. Part I: The Role of Meiosis in Sexual Reproduction
Key Idea: Meiosis produces sex cells that are used in sexual reproduction.

3. Asexual reproduction requires. parent and makes genetically. offspring
Asexual reproduction requires parent and makes genetically offspring. The process of
is used to create the first cell of the offspring.

4. Asexual reproduction requires. one. parent and makes genetically
Asexual reproduction requires one parent and makes genetically offspring. The process of
is used to create the first cell of the offspring.

5. Asexual reproduction requires. one. parent and makes genetically
Asexual reproduction requires one parent and makes genetically identical offspring. The process of
is used to create the first cell of the offspring.

6. Asexual reproduction requires. one. parent and makes genetically
Asexual reproduction requires one parent and makes genetically identical offspring. The process of mitosis is used to create the first cell of the offspring.

7. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as , which are made during the process of meiosis.

8. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis.

9. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis. In the process of , these sex cells fuse, forming the first cell of the offspring, called a .

10. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis. In the process of fertilization , these sex cells fuse, forming the first cell of the offspring, called a .

11. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis. In the process of fertilization , these sex cells fuse, forming the first cell of the offspring, called a zygote .

12. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis. In the process of fertilization , these sex cells fuse, forming the first cell of the offspring, called a zygote . This cell then divides by to produce a multicellular organism.

13. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis. In the process of fertilization , these sex cells fuse, forming the first cell of the offspring, called a zygote . This cell then divides by mitosis to produce a multicellular organism.

14. Sexual reproduction involves two parents (one male and one female) providing sex cells (egg and sperm), also known as gametes , which are made during the process of meiosis. In the process of fertilization , these sex cells fuse, forming the first cell of the offspring, called a zygote . This cell then divides by mitosis to produce a multicellular organism. Because the offspring has DNA from the mother and the father, it is a genetic blend of the parents.

15. Label the arrows of the diagram of sexual reproduction and development.

16. Cell in the ovary of the mother
Egg
Zygote
Cell in the testes of the father
Sperm

17. 46
Cell in the ovary of the mother
Egg
Zygote 46
Cell in the testes of the father
Sperm

18. 46
Meiosis
Cell in the ovary of the mother
Egg
Zygote 46
Meiosis
Cell in the testes of the father
Sperm

19. 46 23
Meiosis
Cell in the ovary of the mother
Egg
Zygote 46
Meiosis
Cell in the testes of the father
Sperm

20. 46 23
Meiosis
Cell in the ovary of the mother
Egg
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

21. 46 23
Meiosis
Cell in the ovary of the mother
Egg
Fertilization
Fertilization
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

22. 46 23
Meiosis
Cell in the ovary of the mother
Egg
Fertilization 46
Fertilization
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

23. 46 23
Meiosis
Cell in the ovary of the mother
Egg
Fertilization 46
Mitosis
Fertilization
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

24. 46 23
Meiosis
Cell in the ovary of the mother
Egg
Fertilization 46
Mitosis
Fertilization
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

25. Why must meiosis and not mitosis be used to make gametes?

26. Why must meiosis and not mitosis be used to make gametes?
Each type of organism has a specific number of chromosomes in its body cells.

27. Why must meiosis and not mitosis be used to make gametes?
Each type of organism has a specific number of chromosomes in its body cells. For example, humans have _ chromosomes in each body cell.

28. Why must meiosis and not mitosis be used to make gametes?
Each type of organism has a specific number of chromosomes in its body cells. For example, humans have 46 chromosomes in each body cell.

29. Why must meiosis and not mitosis be used to make gametes?
Each type of organism has a specific number of chromosomes in its body cells. For example, humans have 46 chromosomes in each body cell.
Meiosis produces gametes with the number of chromosomes as a body cell.

30. Why must meiosis and not mitosis be used to make gametes?
Each type of organism has a specific number of chromosomes in its body cells. For example, humans have 46 chromosomes in each body cell.
Meiosis produces gametes with half the number of chromosomes as a body cell.

31. Why must meiosis and not mitosis be used to make gametes?
As a result of the uniting of the sperm and egg during , the zygote receives half of its chromosomes from the and half from the , resulting in a whole number of chromosomes that is the same as in each of the parents.

32. Why must meiosis and not mitosis be used to make gametes?
As a result of the uniting of the sperm and egg during fertilization , the zygote receives half of its chromosomes from the and half from the , resulting in a whole number of chromosomes that is the same as in each of the parents.

33. Why must meiosis and not mitosis be used to make gametes?
As a result of the uniting of the sperm and egg during fertilization , the zygote receives half of its chromosomes from the mother and half from the , resulting in a whole number of chromosomes that is the same as in each of the parents.

34. Why must meiosis and not mitosis be used to make gametes?
As a result of the uniting of the sperm and egg during fertilization , the zygote receives half of its chromosomes from the mother and half from the father , resulting in a whole number of chromosomes that is the same as in each of the parents.

35. Why must meiosis and not mitosis be used to make gametes?
Changes in this body cell chromosome number can result in disease and even death. For example, one extra copy of the 21st chromosome in human body cells results in Down Syndrome.

36. Using mitosis to make gametes:
Cell in the ovary of the mother
Egg
Zygote
Cell in the testes of the father
Sperm

37. Using mitosis to make gametes:46
Cell in the ovary of the mother
Egg
Zygote 46
Cell in the testes of the father
Sperm

38. Using mitosis to make gametes:46
Mitosis
Cell in the ovary of the mother
Egg
Zygote 46
Mitosis
Cell in the testes of the father
Sperm

39. Using mitosis to make gametes:46 46
Mitosis
Cell in the ovary of the mother
Egg
Zygote 46 46
Mitosis
Cell in the testes of the father
Sperm

40. Using mitosis to make gametes:46 46
Mitosis
Fertilization
Cell in the ovary of the mother
Egg
Fertilization
Zygote 46 46
Mitosis
Cell in the testes of the father
Sperm

41. Using mitosis to make gametes:46 46
Mitosis
Fertilization
Cell in the ovary of the mother
Egg 92
Fertilization
Zygote 46 46
Mitosis
Cell in the testes of the father
Sperm

42. Using meiosis to make gametes:
Cell in the ovary of the mother
Egg
Zygote
Cell in the testes of the father
Sperm

43. Using meiosis to make gametes:46
Cell in the ovary of the mother
Egg
Zygote 46
Cell in the testes of the father
Sperm

44. Using meiosis to make gametes:46
Meiosis
Cell in the ovary of the mother
Egg
Zygote 46
Meiosis
Cell in the testes of the father
Sperm

45. Using meiosis to make gametes:46 23
Meiosis
Cell in the ovary of the mother
Egg
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

46. Using meiosis to make gametes:46 23
Meiosis
Fertilization
Cell in the ovary of the mother
Egg
Fertilization
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

47. Using meiosis to make gametes:46 23
Meiosis
Fertilization
Cell in the ovary of the mother
Egg 46
Fertilization
Zygote 46 23
Meiosis
Cell in the testes of the father
Sperm

48. Part II: Examining Chromosome Number and Cell Type

49. Taking a closer look at chromosome number:
Haploid:

50. Taking a closer look at chromosome number:
Haploid: a gamete, or sex cell, that contains a single set of chromosomes

51. Taking a closer look at chromosome number:
Haploid: a gamete, or sex cell, that contains a single set of chromosomes
Abbreviated as where N is the number of types of chromosomes

52. Taking a closer look at chromosome number:
Haploid: a gamete, or sex cell, that contains a single set of chromosomes
Abbreviated as N where N is the number of types of chromosomes

53. Taking a closer look at chromosome number:
Haploid: a gamete, or sex cell, that contains a single set of chromosomes
Abbreviated as n where N is the number of types of chromosomes
Haploid cells have only one of each type of chromosome.

54. Taking a closer look at chromosome number:
Diploid:

55. Taking a closer look at chromosome number:
Diploid: a cell that contains both sets of chromosomes

56. Taking a closer look at chromosome number:
Diploid: a cell that contains both sets of chromosomes
Abbreviated as where N is the number of types of chromosomes

57. Taking a closer look at chromosome number:
Diploid: a cell that contains both sets of chromosomes
Abbreviated as 2N where N is the number of types of chromosomes

58. Taking a closer look at chromosome number:
Diploid: a cell that contains both sets of chromosomes
Abbreviated as 2N where N is the number of types of chromosomes
Diploid cells have two of each type of chromosome. (Remember di- means two)

59. Homologous chromosomes:

60. Homologous chromosomes: chromosomes that each have a corresponding chromosome from the opposite sex parent

61. Homologous chromosomes: chromosomes that each have a corresponding chromosome from the opposite sex parent
Have similar size, location of the centromere and genes (code for traits)

62. Homologous chromosomes: chromosomes that each have a corresponding chromosome from the opposite sex parent
Have similar size, location of the centromere and genes (code for traits)
Only differ in the sequence of DNA, which determines the specific version of a trait.

63. Homologous chromosomes: chromosomes that each have a corresponding chromosome from the opposite sex parent
Have similar size, location of the centromere and genes (code for traits)
Only differ in the sequence of DNA, which determines the specific version of a trait.
Each homologous pair represents one type of chromosome.

64. Diploid Cell
Example: Body Cell
Haploid Cell
Example: Egg Cell
Chromosome from the mother
Chromosome from the father

65. Taking a closer look at the types of cells in the human body:
Somatic cells:

66. Taking a closer look at the types of cells in the human body:
Somatic cells: any cells forming the body of an organism, excluding sex cells

67. Taking a closer look at the types of cells in the human body:
Somatic cells: any cells forming the body of an organism, excluding sex cells
Are so they contain

68. Taking a closer look at the types of cells in the human body:
Somatic cells: any cells forming the body of an organism, excluding sex cells
Are diploid so they contain

69. Taking a closer look at the types of cells in the human body:
Somatic cells: any cells forming the body of an organism, excluding sex cells
Are diploid so they contain 2 complete sets of chromosomes

70. Taking a closer look at the types of cells in the human body:
Gametes:

71. Taking a closer look at the types of cells in the human body:
Gametes: Sex cells that contain only one set of chromosomes

72. Taking a closer look at the types of cells in the human body:
Gametes: Sex cells that contain only one set of chromosomes
Are so they contain

73. Taking a closer look at the types of cells in the human body:
Gametes: Sex cells that contain only one set of chromosomes
Are haploid so they contain

74. Taking a closer look at the types of cells in the human body:
Gametes: Sex cells that contain only one set of chromosomes
Are haploid so they contain one set of chromosomes, or half the genetic material of the parent

75. Let’s practice with chromosome number:
Armadillos have a haploid number of What is their diploid number?

76. Let’s practice with chromosome number:
Armadillos have a haploid number of What is their diploid number? 64

77. Let’s practice with chromosome number:
Armadillos have a haploid number of What is their diploid number? 64
Houseflies have a diploid number of 12. How many chromosomes are in a fly egg?

78. Let’s practice with chromosome number:
Armadillos have a haploid number of What is their diploid number? 64
Houseflies have a diploid number of 12. How many chromosomes are in a fly egg? 6

79. Let’s practice with chromosome number:
Armadillos have a haploid number of What is their diploid number? 64
Houseflies have a diploid number of 12. How many chromosomes are in a fly egg? 6
Mice have 20 chromosomes in their somatic cells. How many chromosomes are in their gametes?

80. Let’s practice with chromosome number:
Armadillos have a haploid number of What is their diploid number? 64
Houseflies have a diploid number of 12. How many chromosomes are in a fly egg? 6
Mice have 20 chromosomes in their somatic cells. How many chromosomes are in their gametes? 10

81. Karyotype:

82. Karyotype: photograph of chromosomes grouped in order in pairs

83. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so _ are grouped together

84. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so homologous pairs are grouped together

85. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so homologous pairs are grouped together
Humans have 22 pairs of , or chromosomes NOT involved in determining the sex of an individual.

86. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so homologous pairs are grouped together
Humans have 22 pairs of autosomes , or chromosomes NOT involved in determining the sex of an individual.

87. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so homologous pairs are grouped together
Humans have 22 pairs of autosomes , or chromosomes NOT involved in determining the sex of an individual. These chromosomes contain the genes that determine all the traits that don’t determine your sex, such as hair color or whether you are lactose intolerant. They are pairs 1-22 in the karyotype.

88. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so homologous pairs are grouped together
Humans have 22 pairs of autosomes , or chromosomes NOT involved in determining the sex of an individual. These chromosomes contain the genes that determine all the traits that don’t determine your sex, such as hair color or whether you are lactose intolerant. They are pairs 1-22 in the karyotype.
Humans have 1 pair of , or chromosomes that determine the sex of an individual. These are the X and Y chromosomes.

89. Karyotype: photograph of chromosomes grouped in order in pairs
Chromosomes are arranged based on type so homologous pairs are grouped together
Humans have 22 pairs of autosomes , or chromosomes NOT involved in determining the sex of an individual. These chromosomes contain the genes that determine all the traits that don’t determine your sex, such as hair color or whether you are lactose intolerant. They are pairs 1-22 in the karyotype.
Humans have 1 pair of sex chromosomes, or chromosomes that determine the sex of an individual. These are the X and Y chromosomes.

90. Normal human karyotype from a somatic cell

92. Practice Questions
What is the diploid number (2n) of a human cell? chromosomes
What is the haploid number (n) of a human cell? chromosomes
The body cells of males have
The body cells of females have

93. Practice Questions
What is the diploid number (2n) of a human cell? 46 chromosomes
What is the haploid number (n) of a human cell? chromosomes
The body cells of males have
The body cells of females have

94. Practice Questions
What is the diploid number (2n) of a human cell? 46 chromosomes
What is the haploid number (n) of a human cell? 23 chromosomes
The body cells of males have
The body cells of females have

95. Practice Questions
What is the diploid number (2n) of a human cell? 46 chromosomes
What is the haploid number (n) of a human cell? 23 chromosomes
The body cells of males have 46 chromosomes
The body cells of females have

96. Practice Questions
What is the diploid number (2n) of a human cell? 46 chromosomes
What is the haploid number (n) of a human cell? 23 chromosomes
The body cells of males have 46 chromosomes
The body cells of females have chromosomes

97. Phases of Meiosis
Part III

98. Key Ideas
Meiosis involves two rounds of cell division so one cell becomes four cells.
Just like mitosis, meiosis is preceded by interphase.

99. Meiosis I-First round of cell division

100. Meiosis I-First round of cell division
Goes through the 4 stages of division: prophase I, metaphase I, anaphase I and telophase I

101. Meiosis I-First round of cell division
Goes through the 4 stages of division: prophase I, metaphase I, anaphase I and telophase I
Meiosis I involves the separation of

102. Meiosis I-First round of cell division
Goes through the 4 stages of division: prophase I, metaphase I, anaphase I and telophase I
Meiosis I involves the separation of homologous pairs

103. Meiosis I-First round of cell division
Goes through the 4 stages of division: prophase I, metaphase I, anaphase I and telophase I
Meiosis I involves the separation of homologous pairs
It is a reduction division, meaning the cell goes from being diploid to

104. Meiosis I-First round of cell division
Goes through the 4 stages of division: prophase I, metaphase I, anaphase I and telophase I
Meiosis I involves the separation of homologous pairs
It is a reduction division, meaning the cell goes from being diploid to haploid

105. Meiosis I-First round of cell division
Goes through the 4 stages of division: prophase I, metaphase I, anaphase I and telophase I
Meiosis I involves the separation of homologous pairs
It is a reduction division, meaning the cell goes from being diploid to haploid

106. Meiosis I-First round of cell division
To increase diversity, crossing over between homologous chromosomes can occur.

107. Meiosis I:

108. Meiosis I: Prophase I

109. Meiosis I:

110. Meiosis I: Metaphase I

111. Meiosis I:

112. Meiosis I: Anaphase I

113. Meiosis I:

114. Meiosis I: Telophase I

115. Meiosis II: Second round of cell division

116. Meiosis II: Second round of cell division
This is the second round of cell division

117. Meiosis II: Second round of cell division
This is the second round of cell division
NOT proceeded by interphase. The two cells from meiosis I immediately start meiosis II.

118. Meiosis II: Second round of cell division
This is the second round of cell division
NOT proceeded by interphase. The two cells from meiosis I immediately start meiosis II.
Meiosis II involves the separation of

119. Meiosis II: Second round of cell division
This is the second round of cell division
NOT proceeded by interphase. The two cells from meiosis I immediately start meiosis II.
Meiosis II involves the separation of sister chromatids

120. Meiosis II: Second round of cell division
This is the second round of cell division
NOT proceeded by interphase. The two cells from meiosis I immediately start meiosis II.
Meiosis II involves the separation of sister chromatids
The events are similar to those in mitosis, but the resulting 4 cells are haploid.

121. Meiosis II

122. Meiosis II
Prophase II

123. Meiosis II
Prophase II
Metaphase II

124. Meiosis II
Prophase II
Metaphase II
Anaphase II

125. Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II

126. Mitosis creates games that are genetically different from each other.

127. Mitosis creates games that are genetically different from each other
Mitosis creates games that are genetically different from each other. Crossing over can increase the variety of gametes that are made in meiosis.

128. Mitosis creates games that are genetically different from each other
Mitosis creates games that are genetically different from each other. Crossing over can increase the variety of gametes that are made in meiosis.
Crossing over :

129. Mitosis creates games that are genetically different from each other
Mitosis creates games that are genetically different from each other. Crossing over can increase the variety of gametes that are made in meiosis.
Crossing over : process when chromosomes exchange portions of chromatids, results in an exchange of alleles, producing a new combination

130. Mitosis creates games that are genetically different from each other
Mitosis creates games that are genetically different from each other. Crossing over can increase the variety of gametes that are made in meiosis.
Crossing over : process when chromosomes exchange portions of chromatids, results in an exchange of alleles, producing a new combination
Why is increased genetic variety important?

131. Mitosis creates games that are genetically different from each other
Mitosis creates games that are genetically different from each other. Crossing over can increase the variety of gametes that are made in meiosis.
Crossing over : process when chromosomes exchange portions of chromatids, results in an exchange of alleles, producing a new combination
Why is increased genetic variety important?
The more diversity there are amongst the offspring, the more likely the offspring are to survive changing environmental conditions. If everyone was exactly the same, everyone could be killed by the same type of sickness, disease or climatic change.

132. Prophase I
In interphase, the cells have already replicated their DNA, forming a duplicate chromosome
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad
Centrioles moves to opposite ends of cell
Nuclear membrane dissolves
Crossing over: process when chromosomes exchange portions of chromatids, results in an exchange of alleles, producing a new combination

133. Meiosis in Action
Meiosis in action

134. Problems With Meiosis
Nondisjunction:

135. Problems With Meiosis
Nondisjunction: error in meiosis in which homologous chromosomes fail to separate

136. Problems With Meiosis
Nondisjunction: error in meiosis in which homologous chromosomes fail to separate
Result:

137. Problems With Meiosis
Nondisjunction: error in meiosis in which homologous chromosomes fail to separate
Result: Offspring end up with three copies of a chromosome instead of 2 (Ex. Down syndrome)

138. Nondisjunction in Meiosis I & II

139. Comparing Mitosis and Meiosis
Where does it happen?
Purpose?
Results?

140. Comparing Mitosis and Meiosis
Where does it happen?
Somatic cells
Purpose?
Results?

141. Comparing Mitosis and Meiosis
Where does it happen?
Somatic cells
Gametes
Purpose?
Results?

142. Comparing Mitosis and Meiosis
Where does it happen?
Somatic cells
Gametes
Purpose?
To create cells in order to undergo growth, repair or asexual reproduction
Results?

143. Comparing Mitosis and Meiosis
Where does it happen?
Somatic cells
Gametes
Purpose?
To create cells in order to undergo growth, repair or asexual reproduction
To create cells with half the genetic information to prepare for sexual reproduction
Results?

144. Comparing Mitosis and Meiosis
Where does it happen?
Somatic cells
Gametes
Purpose?
To create cells in order to undergo growth, repair or asexual reproduction
To create cells with half the genetic information to prepare for sexual reproduction
Results?
2 identical diploid daughter cells

145. Comparing Mitosis and Meiosis
Where does it happen?
Somatic cells
Gametes
Purpose?
To create cells in order to undergo growth, repair or asexual reproduction
To create cells with half the genetic information to prepare for sexual reproduction
Results?
2 identical diploid daughter cells
4 genetically unique haploid cells