Cell Cycle-Mitosis, Sexual Reproduction-Meiosis Inheritance-Genetics

1. Cell Cycle-Mitosis,Sexual Reproduction-Meiosis& Inheritance-Genetics November 17, 2007 Bio099 Martini Pages 95-101, 1036-1038, 1050-1051, 1099-1105

2. The life of a cell The human body has about 75 trillion cells, which all start from a single cell. Depending on the type, a cell may live for hours or years. Cellular division is essential for life.

3. Cell Division and Chromosome Number Humans somatic cells contain 23 pairs of chromosomes. Homologous pairs paternal (father) maternal (mother) Because somatic cells contain 2 copies of each chromosome they are called diploid (2n).

4. Cell Division Mitosis (used during somatic cell division) Diploid to Diploid creates 1 new somatic daughter cell parent and daughter cell are genetically identical Meiosis (used during production of sex cells) Diploid to Haploid (1 copy of chromosomes) creates 4 reproductive cells (eggs or sperm) new combination of chromosomes (mix of mom and dad)

5. The Life Cycle of a Somatic Cell

6. Interphase G0 phase A cell that is in this phase is NOT preparing to divide, but instead is carrying out specialized functions.

7. Interphase G1 phase This first stage on the way to cell division involves growth, organelle production and protein synthesis.

8. Interphase S phase A cell in this phase is duplicating its genome by replicating all its DNA to make copies of each chromosome 1 duplicated chromosome has 2 chromatids (see picture below)

9. Interphase G2 phase A brief period in which the cell makes more proteins. At this time the centriole pairs are replicated (resulting in 2 pair).

10. Why does the cell duplicate the centrioles? The cell has to create a cytoskeleton structure for the chromosomes to attach to during mitosis. This structure is called the Spindle Apparatus and it is made from microtubules that project from the centrioles.

11. M Phase Mitosis: prophase metaphase anaphase telophase Cytokinesis

12. Review: Cell Cycle A cell that is not preparing to divide is in which phase?

13. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase

14. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase A cell that is replicating its DNA is in which phase?

15. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase A cell that is replicating its DNA is in which phase? S phase

16. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase A cell that is replicating its DNA is in which phase? S phase In which phase are the centrioles replicated?

17. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase A cell that is replicating its DNA is in which phase? S phase In which phase are the centrioles replicated? G2 phase

18. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase A cell that is replicating its DNA is in which phase? S phase In which phase are the centrioles replicated? G2 phase What happens during G1?

19. Review: Cell Cycle A cell that is not preparing to divide is in which phase? G0 phase A cell that is replicating its DNA is in which phase? S phase In which phase are the centrioles replicated? G2 phase What happens during G1? preparation for division (growth, organelle production and protein synthesis)

20. Mitosisthe process of organizing and distributing nuclear DNA Early Prophase the chromatin begins to condense into chromosomes

21. Mitosis Late Prophase one of the centriole pairs moves to the opposite side of the cell. microtubules begin to grow from the centrioles building the spindle apparatus. the nuclear envelope begins to dissolve.

22. Mitosis Transition to Metaphase the spindle apparatus forms completely and the chromosomes attach

23. Mitosis Metaphase the chromosomes line up along the equator of the cell

24. Mitosis Anaphase the sister chromatids are taken to opposite poles of the

25. Mitosis Telephase The chromosomes decondense back into chromatin Nuclear membranes form around each set of unduplicated chromosomes

26. Cytokinesis The actual division of the cytoplasm usually occurs toward the end of telephase.

27. Somatic cell division results in two identical cells

28. Mitosis is regulated by growth factors

29. Mitosis is inhibited by suppressor genes For example: p53

30. Cancer When the rate of cell division (mitotic rate) is greater than that of cell death in a tissue

31. Tumors A mass of abnormal cells benign = encapsulated within tissue epithelium malignant = spread to surrounding tissue

32. Malignant Tumors When cancer cells spread from their region of origin (primary tumor), this spreading process is called invasion. Eventually these malignant cells may travel to other tissues and form secondary tumors, this is known as metastasis. Oncogenes: the name given to mutated genes involved in cell growth that can cause cancer

33. Review: Mitosis What is the mitotic phase?

34. Review: Mitosis What is the mitotic phase?

35. Review: Mitosis What is the mitotic phase?

36. Review: Mitosis What is the mitotic phase?

37. Review: Mitosis What is the mitotic phase?

38. Review: Mitosis What is the mitotic phase?

39. Review: Mitosis What is the mitotic phase?

40. Review: Mitosis What is the mitotic phase?

41. Review: Mitosis What is this called and in which mitotic phase does it occur?

42. Sexual Reproduction: creating genetic diversity

43. Sexual Reproduction: creating genetic diversity

44. An overview:from germ cell to babies Germ Cells � diploid cells of the reproductive organs. Gametes � haploid cells (sperm/egg = 23 chromosomes) made from germ cells by a process called meiosis. babies � conceived when the nuclei of sperm and egg join to make 46 total chromosomes (23 homologous pair)

45. Germ Cells:homologous chromosomes All somatic cells have 46 chromosomes (23 homologous pairs), one copy of each pair is inherited from the mother and the other from the father.

46. Because of homologous chromosomes there are 2 copies of each gene.

47. One gene can come in different varieties. Allele: variant forms of the same gene. Can you think of an example of a gene that has more than 1 allele?

48. Sexual Reproduction Shuffles Alleles Through sexual reproduction, offspring inherit new combinations of alleles, which lead to variations in traits

49. Gamete Formation Gametes are sex cells (sperm, eggs) Gametes are formed when germ cells in reproductive organs undergo meiosis.

50. Two important things happen during meiosis The number of chromosomes is cut in half (46 to 23) The alleles are rearranged so that any offspring produced are genetically different from the parents.

51. chromosome number in gametes n is equal to the total number of chromosomes in a cell Germ cells (like somatic cells) are diploid (2n) Gametes are haploid (1n)

52. How does 1 germ cell (2n) become 4 gametes (1n)? Two consecutive cell divisions, but only 1 replication of the DNA 1. Meiosis I 2. Meiosis II

53. Before Meiosis begins, the DNA of the germ cell is replicated during interphase

54. Meiosis I Prophase I Each duplicated chromosome pairs with homologue (mom�s copy with dad�s copy) Homologues form tetrads during synapsis and swap segments (cross over) to increase genetic variation Each chromosome becomes attached to spindle

55. Crossing Over

56. Outcome of Crossing Over After crossing over, a chromosome will contain both maternal and paternal segments Creates new allele combinations in offspring

57. Meiosis I Metaphase I The spindle apparatus is fully formed the homologous chromosomes (tetrads) line up randomly along the equator of the cell

58. Random Alignment In Meiosis I the chromosomes line up at the equator randomly This means that the genetic contributions from mom and dad can be mixed up in the gametes.

59. Meiosis I Anaphase I homologous chromosomes segregate the sister chromatids remain attached

60. Meiosis I Telophase I chromosomes arrive at opposite ends of the cell and cytokinesis separates the cytoplasm

61. Meiosis I results in: 2 genetically different diploid (2n) cells

62. Prophase II Microtubules attach to the kinetochores of the duplicated chromosomes

63. Metaphase II Duplicated chromosomes line up at the spindle equator, midway between the poles

64. Anaphase II Sister chromatids separate to become independent chromosomes

65. Telophase II The chromosomes arrive at opposite ends of the cell A nuclear envelope forms around each set of chromosomes The result is four haploid cells (gametes)

66. Mitosis vs. Meiosis

67. Oogenesis

68. Spermatogenesis

69. Fertilization Male and female gametes uniteand their nuclei fuse together combining the chromosomes. Fusion of two haploid nuclei produces a diploid nucleus in the zygote

70. Factors that contribute to variation among Offspring Crossing over during prophase I Random alignment of chromosomes at metaphase I Random combination of gametes at fertilization

71. Review: Chromosomes How many chromosomes do human somatic cells have?

72. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs)

73. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs) How about gametes?

74. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs) How about gametes? 23

75. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs) How about gametes? 23 What are homologous chromosomes?

76. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs) How about gametes? 23 What are homologous chromosomes? chromosomes that have the same genes in the same loci (location)

77. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs) How about gametes? 23 What are homologous chromosomes? chromosomes that have the same genes in the same loci (location) how might they differ?

78. Review: Chromosomes How many chromosomes do human somatic cells have? 46 (23 pairs) How about gametes? 23 What are homologous chromosomes? chromosomes that have the same genes in the same loci (location) how might they differ? the allele type of the genes might differ

79. Review: Meiosis In what phase of meiosis do the homologous chromosomes synapse?

80. Review: Meiosis In what phase of meiosis do the homologous chromosomes synapse? phrophase I

81. Review: Meiosis In what phase of meiosis do the homologous chromosomes synapse? phrophase I What are the synapsed homologues called?

82. Review: Meiosis In what phase of meiosis do the homologous chromosomes synapse? phrophase I What are the synapsed homologues called? tetrads

83. Review: Meiosis In what phase of meiosis do the homologous chromosomes synapse? phrophase I What are the synapsed homologues called? tetrads What event occurs during synapsis that increases variation of the offspring?

84. Review: Meiosis In what phase of meiosis do the homologous chromosomes synapse? phrophase I What are the synapsed homologues called? tetrads What event occurs during synapsis that increases variation of the offspring? crossing over

85. Review: Meiosis During Metaphase I the tetrads line up on the equator randomly; why is this significant? because it increases variation among the offspring

86. Review: Meiosis How many gametes are made from one germ cell during Meiosis?

87. Review: Meiosis How many gametes are made from one germ cell during Meiosis? four

88. Review: Meiosis How many gametes are made from one germ cell during Meiosis? four How many times is the DNA replicated?

89. Review: Meiosis How many gametes are made from one germ cell during Meiosis? four How many times is the DNA replicated? once

90. Review: Meiosis How many gametes are made from one germ cell during Meiosis? four How many times is the DNA replicated? once How many chromosomes does each gamete contain?

91. Review: Meiosis How many gametes are made from one germ cell during Meiosis? four How many times is the DNA replicated? once How many chromosomes does each gamete contain? 23

92. Inheritance Martini pgs 1099-1105

93. Patterns of disease inheritance had been known for 1000s of years This is a pedigree showing the inheritance of one of the best known genetic diseases, haemophilia, in the royal family. The inheritance of haemophilia is now well understood This is a pedigree showing the inheritance of one of the best known genetic diseases, haemophilia, in the royal family. The inheritance of haemophilia is now well understood

94. Mendelian Genetics Segregation Dominance Independent assortment Mendel summarised his findings in two laws of inheritance.Mendel summarised his findings in two laws of inheritance.

95. Mendel�s experiments

96. Mendel�s data

97. Mendel�s law of segregation Somatic cells have only two alleles for a Mendelian trait. A gamete contains one allele, randomly chosen from the two somatic alleles. TERMINOLOGY When the two alleles are the same (e.g., BB) it is called homozygous When the two alleles are different (e.g., Bb) it is called heterozygous. The Punnet Square is a tool to figure out the probability of inheriting a specific trait. Autosomal e.g. iris pigment cellAutosomal e.g. iris pigment cell

98. Mendel�s law of segregation One of the two possible alleles will be displayed dominantly. The uppercase letter is dominant (visible) The lowercase letter is recessive (hidden) Clearly many traits are much more complicated than this, but Mendel concentrated on simple traits because these were the ones that allowed the fundamental laws to be deduced from which the theory behind more complex traits was later developed.Clearly many traits are much more complicated than this, but Mendel concentrated on simple traits because these were the ones that allowed the fundamental laws to be deduced from which the theory behind more complex traits was later developed.

99. Mendel�s law of segregation A person that is heterozygous for a trait (Bb) will only display the dominant allele.

100. Terminology� Genotype: the states of the two alleles at one or more locus associated with a trait (the genetic code of the gene). Phenotype: the state of the observable trait (the outward appearance). phenotype is fn of genotype, environment and agephenotype is fn of genotype, environment and age

101. Major Forms of Inheritance

102. Major Forms of Inheritance:dominant inheritance

103. Pretend we only have brown and blue eyes for this example: Brown dominant: BB, Bb Blue recessive: bb A common game that parents-to-be playA common game that parents-to-be play

104. Dominant Inheritance Go through pedigree. Squares mean males, circles women, diamonds usually mean unborn children of unknown sex. If we know nothing about the child, the prob that it will have blue eyes is the population frequency, which in the UK is about �. However, we do know the eye colour of relatives of the child. Ideally, we would like to know the genotypeGo through pedigree. Squares mean males, circles women, diamonds usually mean unborn children of unknown sex. If we know nothing about the child, the prob that it will have blue eyes is the population frequency, which in the UK is about �. However, we do know the eye colour of relatives of the child. Ideally, we would like to know the genotype

105. Dominant Inheritance

106. Dominant Inheritance

107. Dominant Inheritance

108. Dominant Inheritance

109. Dominant Inheritance

110. Dominant Inheritance

111. Dominant Inheritance

112. Huntington�s Disease A disease with dominant inheritance

113. Major Forms of Inheritance:recessive inheritance

114. Recessive Inheritance

115. Major Forms of Inheritance:codominance

116. Codominanance Two alleles are equally dominant and are both displayed in the phenotype of the heterozygote. For example: Blood type Blood type is also an Example of a trait that has more than 2 alleles: multiple allele trait

117. Major Forms of Inheritance:incomplete dominance

118. Incomplete Dominance alleles appear to blend in the heterozygote. For example: Snapdragon color

119. Major Forms of Inheritance:incomplete dominance

120. Polygene Inheritance When multiple genes impact the phenotype of a trait: Examples: Skin color Height Body weight

121. Major Forms of Inheritance

122. Sex chromosomes X Chromosome Considerably larger than Y Has more genes than Y Carried by all oocytes Y Chromosome Includes dominant alleles specifying that the individual will be male Not present in females

123. X-linked Inheritance

124. Chromosome abnormalities Non-disjunction occurs when either homologous chromosomes fail to separate during anaphase I of meiosis, or sister chromatids fail to separate during anaphase II.

125. Genetic Testing for Specific Conditions Take a sample (blood/amniotic fluid, mouth swab) Use staining of chromosomes to locate any chromosome abnormalities or use matching DNA sequences or antibodies to detect gene abnormalities