2. Mitosis  Why do cells need to divide?

5. Recap…  Cell theory…  Cells are the basic structural and functional unit of life (Hooke)  All living things (plants, animals, fungi, bacteria, protista) are made of cells (Schleiden, Schwann, Van Leewoehoek)  Cells come from pre-existing cells (Virchow)

6. Overview  Why do cells need to divide?  Repair, growth, development  Types of reproduction  Sexual Reproduction  Genetically different  2 parents  Takes time to develop, better chance of survival  More chance of mutation  Process begins by making gametes…Uses MEIOSIS  asexual  Genetically identical  One parent  Many offspring very quickly  Less chance of mutations  (by MITOSIS)

7. DNA  Blueprint of life, nucleic acid  Chromatin  Granular genetic material, spread out in nucleus of non-dividing cells  Chromosomes  Condensed genetic material, in dividing cells  Sister chromatids  Identical copies of Chromosomes joined by a centromere (“centro-” middle)

10. Humans  46 chromosomes  46 sister chromatids  One from your mom, one from your dad

11. Cell Cycle: Life of a Cell

12. Cell Cycle  Interphase  90 % of cell’s life, non dividing  G1 phase  Grows, makes organelles  S phase  DNA Synthesis…DNA replicates  G2 phase  Cell prepares to divide, makes sure it has all important organelles for division  M phase  When the cytoplasm and nucleus of the cell divides

13. Cell Cycle  There are check points in G1, S, and G2  Make sure cell is ready to move onto the next phase (has all necessary organelles, copied DNA, etc.)  Once the cell has past the G1 checkpoint, it will complete the cell cycle  Some cells stay in the G1 phase all their life (muscle cell, brain cells)

14. Regulators of Cell Cycle  Cyclins  Protein that regulates the timing of the cell cycle in eukaryotic cells  Levels of cyclins rise and fall throughout the cell cycle  Cyclin-dependent Kinases (cdks)  Enzymes that are activated when they bind with cyclin and they make the cell cycle continue

17. Regulators  Internal  Factors within the cell that control cell cycle  Cyclin and CDKs  Allow cell cycle to proceed only when certain processes have occurred  Replication of chromosomes  Chromosome Attachment to spindle before anaphase  External  Factors Outside the cell  Growth factors  molecules that bind to cell surface that signal cell to divide  Similar cells have molecules that have opposite effect so that when it becomes to crowded, cells stop dividing

22. M-phase  Consists of mitosis and cytokinesis  Mitosis  Process by which the nucleus of a cell divides  One parent cell makes two identical daughter cells  This is how organisms repair tissue and grow and develop  Cytokinesis-division of the cytoplasm

24. Depending on cell type…  Mitosis can take a few minutes or a few days  Muscle cells (non-dividing)  Nerve cells (non-dividing)  Skin cells (divide all the time)  Digestive Tract cells (divide all the time)

25. Life Span of Some Human Cells Cell typeLife spanCell division Lining of esophagus2-3 daysCan divide Lining of small intestine1-2 daysCan divide Lining of the large intestine 6 daysCan divide Red blood cellsLess than 120 daysCannot divide White blood cells10 hours to decadesMany do not divide Smooth muscleLong-livedCan divide Cardiac (heart) muscleLong-livedCannot divide Skeletal muscleLong-livedCannot divide Neurons (nerve) cellsLong-livedMost do not divide

28. Prophase  50-60% of time  Chromosomes become visible  Centrioles develop in cytoplasm near nuclear envelope  Centrioles separate and migrate to opposite ends of nuc. Env.  Centrosome  Region where Centrioles are found  Organize the “spindle”  Fan like microtubule structure that helps separate chromosomes  Plants do NOT have Centrioles

31. End of prophase  Chromosomes coil together tightly  Nucleolus disappears  Nuclear envelope breaks down

32. Metaphase  Few minutes  Chromosomes line up in middle (M in metaphase  MIDDLE)  Microtubules connect centromere of each chromosome to the 2 poles of spindle

36. Anaphase  Centromeres joining sister chromatids separate and become individual chromosomes  They are dragged by fibers to opposite poles  Ends when chromosomes stop moving

40. Telophase  Opposite of prophase  Condensed chromosomes disperse into tangle of material  Nuclear envelope reforms  Spindle breaks apart  Nucleolus becomes visible  At the end  2 identical nuclei in one cell

44. Cytokinesis  Happens at the same time as Telophase  Division of cytoplasm  Animal Cells  Cell membrane drawn inward until it pinches off and forms 2 id daughter cells  Plant Cells  Cell plate forms between nuclei  Cell Plate develops into separate membrane  Cell wall appears

51. MEIOSIS

52. MEIOSIS

53.  Gregor Mendel  1822  Austrian monk  University of Vienna  In charge of the Garden

54. What Gregor Mendel Knew…  Each organism must inherit a single copy of every gene from each of its “parents”  Each of the organisms gametes must contain just one set genes  When gametes are formed, there must be a process that separates the 2 sets of genes so each gamete gets one set

55. Karyotype  A photograph of a person's chromosomes, arranged according to size

60. Chromosome Number  Homologous chromosomes  Chromosome that has a corresponding chromosome from the opposite-sex parent  Fruit fly has 8 chromosomes  4 from mom  4 from dad

62.  Before meiosis 1, each chromosome is replicate (s-phase of cell cycle)  Tetrad  STRUCTURE MADE WHEN EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME  4 CHROMATIDS IN A TETRAD

63. Diploid  Di= two sets  Cell that contains both sets of homologus chromosomes  Cell contains  2 complete sets of chromosome  2 complete sets of genes  Number of chrms in diploid cell represented by 2N  For Drosophilia (fruit fly) 2N=8  Mendel said:  Each adult cell contains two copies of each gene

64. Haploid  Means “one set”  Refers to cells that contain only one set of chromosomes  Gametes (sex cells)  Represented by N  Drosophilia fruit fly  N=4

65. How are haploid (N) gametes made from diploid (2N) cells?

66. Meiosis  Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell

67. Meiosis 2222 distinct stages MMMMeiosis I AAAA diploid cell enters here MMMMeiosis II AAAAt the end of this, the diploid cell that entered meiosis has become 4 haploid cells

70. Meiosis I  Before meiosis 1, each chromosome is replicate  Tetrads line up like the sister chromatids did in mitosis  What happened in mitosis?  PMAT  Tetrad  STRUCTURE MADE WHEN EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME  4 CHROMATIDS IN A TETRAD

71. Prophase 1  Each chromosome pairs with its homologous chromosome making a tetrad  As they pair up in tetrads, chromosomes exchange portions of their chromatids in the process …. CROSSING OVER  First way genetic variation in gametes is achieved

72. Crossing Over

74. Metaphase1  Homologous pairs line up in center of cell RANDOMLY…called Independent Assortment  Lead s to genetic variation (in addition to crossing over) Anaphase 1 The spindles pull homologous chromosomes apart to opposite poles/ends Telophase 1 Nuclear membranes form and cell separates into two new cells

76. Now what do we have?  2 new daughter cells  Are they identical to the parents?  No  Let’s say the parent started with 8 chromosomes  Each daughter cell has 8 chromosomes but they are different because of crossing-over  Each daughter cell has a set of chromosomes and alleles different from each other and different from the parent diploid cell

77. Meiosis II  Unlike Mitosis, Neither cell goes through a round of chromosome replication

78. Prophase II  Meiosis I resulted in 2 “seemingly” diploid cells  Remember they are genetically different b/c of crossing over in prophase I  We still need to cut this number in half to reach our goal of 4 haploid cells

79. Metaphase 2  Chromosomes line up in middle Anaphase 2 Sister chromatids separate and move to opposite poles Telophase 2 Meiosis II results in 4 haploid (N) daughter cells

83. Gamete Formation  Male  Haploid gametes produced by meiosis are called spermatozoa  Spermatogenesis begins at puberty and continues throughout one’s life  Under hormone and environmental control  Female  Haploid gamete produced by meiosis is called an oocyte  Cell divisions at the end of meiosis one and two are uneven so one cell gets most of the cytoplasm (the EGG) and the other three are called polar bodies (don’t participate in reproduction)  IMPORTANT!  Female gametes are stuck in Prophase 1 until puberty  Complete Meiosis 1 every month and the secondary is released from ovary  Female gametes only reach and complete meiosis 2 if they are fertilized

93. Mitosis vs. Meiosis  Mitosis  Results in the production of two genetically identical DIPLOID cells  Daughter cells have sets of chromosomes identical to each other and to parent cell  MITOSIS allows body to grow and replace other cells  Asexual reproduction  Meiosis  Results in four genetically different HAPLOID cells  MEIOSIS is how sexually reproducing organisms make gametes

95. Cancer  Accounts for 1 in 4 deaths in developed countries  More than 100 different forms of cancer  Lung cancer=1 in 17 of all deaths in Britain in the 1990’s  Most common cancer in men-lung  Most common form of cancer in women- breast

96. Cancer  A disease that is the result of uncontrolled mitosis  Tumor-irregular mass of cells created by uncontrolled mitosis

97. Origin of Cancer  Caused by changes in genes that control cell division  Mutation- a change in any gene  Not unusual  Most mutated cells are either crippled in some way that results in their early death or they are destroyed by the body’s immune system  Cancer cells bypass both these fates of mutated cells  Oncogene- term for mutated gene that causes cancer  Onkos in Greek means “mass” or “Bulk”

98. Cancer  Although mutation may have occurred in one cell, it can be passed down to all of this one cells’ descendents  By the time it is detected, a typical tumor consists of about a thousand million cells

99.  Mutagen  A factor that brings about any mutation  Things can be described as mutagenic  Carcinogen  Anything agent that causes cancer  These can described as carcinogenic  Some mutagens are carcinogenic  Factors that increase mutation rates (thus cancer) are as follows: 1.Ionizing Radiation 2.Chemical 3.Viral Infections 4.Hereditary predisposition

100. Ionizing Radiation  X-rays, gamma rays, particles of a decaying radioactive element  Creates the formation of damaging ions inside cells that break DNA strands  UV light also breaks the DNA strands (but it does not cause the formation of ions)  Depletion of the ozone layer is becoming a concern  Leads to more UV radiation hitting Earth’s surface=increase risk to skin cancer

101. Chemicals  Chemical compounds found in many consumer products  25% of all cancers in developed countries are caused by the carcinogens in tar of tobacco smoke  Certain dyes (aniline) are well-known carcinogens

102. Viral Infections  Viruses are genetic material and protein  Cancer viruses are estimated to cause 15 to 20 percent of all cancers in humans  Viruses that cause cancer usually carry oncogenes, or regulatory genes that can become oncogenes  The tumor viruses change cells by integrating their genetic material with the host cell’s DNA via a permanent insertion mechanism  This differs depending on whether the nucleic acid in the virus is DNA or RNA  In DNA viruses, the genetic material can be directly inserted into the host's DNA  RNA viruses must first transcribe RNA to DNA and then insert the genetic material into the host cell's DNA.

103. Viruses and Cancer  DNA Viruses  The Epstein-Barr virus has been linked to Burkitt's lymphoma  Infects B cells and epithelial cells  Causes mononucleosis, but can also cause a few different types of lymphoma and nasopharyngeal cancer  The hepatitis B virus has been linked to liver cancer in people with chronic infections  Human papilloma viruses have been linked to cervical cancer  RNA Viruses  Human T lymphotrophic virus type 1 (HTLV-I), a retrovirus, has been linked to T-cell leukemia  The hepatitis C virus has been linked to liver cancer in people with chronic infections

104. Hereditary disposition  Genetic link based on studying patterns in family members  Disease itself is not inherited but susceptibility to the factors that can cause the disease are inherited  Some forms of cancer are believed to be caused by the inheritance of one faulty gene  Example: Retinoblastoma…caused by error on chromosome 13  Starts in both eyes during childhood and spreads to brain causing blindness and death if left untreated

105. Tumors  Small groups of tumor cells are called primary growths  2 types  Benign tumors  Tumors that do not spread from site of origin  They can compress and displace other tissues, causing discomfort and even death  Warts, ovarian cysts, brain tumors  Malignant (cancerous) tumors  Dangerous  Spread throughout the body, invading and destroying other tissues  Interfere with normal functioning of the area they have started to grow  Mutated cells break off the tumor and enter either the blood or lymph via vessel formation and spread all over the body creating secondary growths  METASTASIS is the spread of cancer from the origin to other parts of the body  most dangerous form of caner…can be very difficult to find secondary growths and remove them  Both benign and malignant tumors involve a huge drain on the human body due to the high demand for nutrients that is created by the rapid and continual cell division

109. Genes

111. Old meiosis slides

112.  Gregor Mendel  1822  Austrian monk  University of Vienna  In charge of the Garden

113. What Gregor Mendel Knew…  Each organism must inherit a single copy of every gene from each of its “parents”  Each of the organisms gametes must contain just one set genes  When gametes are formed, there must be a process that separates the 2 sets of genes so each gamete gets one set

114. Karyotype  A photograph of a organism’s chromosomes, arranged according to size

119. Chromosome Number  Homologous chromosomes  Chromosome that has a corresponding chromosome from the opposite-sex parent  Fruit fly has 8 chromosomes  4 from mom  4 from dad

120. Diploid  Di= two sets  Cell that contains both sets of homologus chromosomes  Cell contains  2 complete sets of chromosome  2 complete sets of genes  Number of chrms in diploid cell represented by 2N  For Drosophilia (fruit fly) 2N=8  Mendel said:  Each adult cell contains two copies of each gene

121. Haploid  Means “one set”  Refers to cells that contain only one set of chromosomes  Gametes (sex cells)  Represented by N  Drosophilia fruit fly  N=4

122. How are haploid (N) gametes made from diploid (2N) cells?

123. Meiosis  Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell

124. Meiosis 2222 distinct stages MMMMeiosis I AAAA diploid cell enters here MMMMeiosis II AAAAt the end of this, the diploid cell that entered meiosis has become 4 haploid cells

127. Meiosis I  Before meiosis 1, each chromosome is replicate  Then they divide like in mitosis  What happened in mitosis?  PMAT  Tetrad  STRUCTURE MADE WHEN EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME  4 CHROMATIDS IN A TETRAD

128. Prophase 1  Each chromosome pairs with its homologous chromosome making a tetrad  As they pair up in tetrads, chromosomes exchange portions of their chromatids in the process …. CROSSING OVER

129. Crossing Over

131. Metaphase1  Spindle fibers attach to chromosomes Anaphase 1 The spindles pull homologous chromosomes apart to opposite poles/ends Telophase 1 Nuclear membranes form and cell separates into two new cells

133. Now what do we have?  2 new daughter cells  Are they identical to the parents?  No  The parent has 4 chromosomes  Each daughter cell has 4 chromosomes but they are different because of crossing-over  Each daughter cell has a set of chromosomes and alleles different from each other and different from the parent diploid cell

134. Meiosis II  Unlike Mitosis, Neither cell goes through a round of chromosome replication  Each cell’s chromosome has 2 chromatids

135. Prophase II  Meiosis I resulted in 2 “seemingly” diploid cells  Remember they are genetically different b/c of crossing over in prophase I  We still need to cut this number in half to reach our goal of 4 haploid cells

136. Metaphase 2  Chromosomes line up in middle Anaphase 2 Sister chromatids separate and move to opposite poles Telophase 2 Meiosis II results in 4 haploid (N) daughter cells 4 daughter cells contain haploid number of chromosomes, just 2 each

139. Gamete Formation  Male  Haploid gametes produced by meiosis are called sperm  Female  Haploid gamete produced by meiosis is called an egg  Cell divisions at the end of meiosis one and two are uneven so one cell gets most of the cytoplasm (the EGG) and the other three are called polar bodies (don’t participate in reproduction)

145. Mitosis vs. Meiosis  Mitosis  Results in the production of two genetically identical DIPLOID cells  Daughter cells have sets of chromosomes identical to each other and to parent cell  MITOSIS allows body to grow and replace other cells  Asexual reproduction  Meiosis  Results in four genetically different HAPLOID cells  MEIOSIS is how sexually reproducing organisms make gametes

149. Genes

152. Microscope Lab Analysis  Mitosis/Meiosis Microscope Lab  Lab notebooks Title “Cell Division Microscope Lab”  MUST sketch each stage and label the power  Label slide name  Stage of mitosis or meiosis  Power of the objective used to observe cell  Need to observe each stage of mitosis and meiosis