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by: Paige holmes

9/24/15 BIOL 1141

Paige holmes
GPA 3.2
Kenneth Mason

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Here are the lecture notes from 9/24/15!
Kenneth Mason
Class Notes
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This 6 page Class Notes was uploaded by Paige holmes on Monday September 28, 2015. The Class Notes belongs to BIOL 1141 at University of Iowa taught by Kenneth Mason in Winter2015. Since its upload, it has received 61 views.

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Date Created: 09/28/15
92415 Animal biology The cell cycle is an orderly set of stages from the rst cell division of a eukaryotic cell to the time the resulting daughter cell divides 0 Just prior to the next cell division Cells grow larger Number of organelles double DNA is replicated o The major stages of the cycle lnterphase includes several stages Mitotic stage mitosis and cytokinesis lnterphase Most of the cell cycle is spent in interphase Cell performs its usual functions Time spent in interphase varies by cell Nerve and muscle cells do not complete the cell cycle remain in the GO stage lnterphase consists of 61 S and 62 phases It takes up 90 of the cell cycle 61 phase 0 Cell is in recovery from previous division 0 Cells doubles its organelles 0 Cell grows in size 0 Cell accumulates raw materials for DNA synthesis S phase 0 DNA replication takes place 0 Proteins associated with DNA are synthesized o Chromosomes enter S phase with 1 chromatid each 0 Chromosomes leave S phase with 2 identical chromatids sister chromatids each 0 Sister chromatids remain attached until they are separated during mitosis 62 Phase M mitotic phase includes Mitosis 0 Nuclear division 0 Daughter chromosomes distributed by the mitotic spindle to two daughter nuclei Cytokinesis 0 Division of the cytoplasm results in two genetically identical daughter cells Control of the cell cycle A signal is a molecule that in uences the activities of a cell The cell cycle is controlled by internal AND external signals 0 External signals Growth factors signaling proteins received at the plasma membrane 0 Internal signals Family of proteins called cyclins that increase and decrease as the cell cycle continues 0 Speci c cyclins must be present for the cell to proceed from one stage to the next 0 Without cyclins the cycle stops at 61 M or 62 checkpoints o Apoptosis programmed cell death It involves a sequence of cellular events that bring about the destruction of the cell Apoptosis is caused by enzymes called caspases Mitosis and apoptosis are opposing forces Cell division and apoptosis occur throughout our lifetimes to maintain the body s homeostasis An abnormal cell that could become cancerous or a virus infected cell are cells that die through apoptosis 92 The eukaryotic chromosome 0 Contains a single DNA molecule double helix DNA is associated with histones DNA and histone proteins are collectively called chromatin DNA wound around an 8 histone core is called a nucleosome which appears as a bead The string quotfoldsquot into a compact zigzag structure It is loosely coiled Euchromatin represents the active chromatin that can be transcribed by RNA polymerase and transcription factors A more highly compact form of chromosome is heterochromatin Inactive chromosome 0 Genes hardly ever transcribed Compact chromosomes more easily moved than extended chromatin Most chromosomes have both compaction levels 93 mitosis and chromosomes 0 Eukaryotic cell division involves mitosis nuclear division and cytokinesis division of cytoplasm 0 During mitosis sister chromatids are separated and distributed to daughter cells 0 Before mitosis begins Chromatin condenses coils into distinctly visible chromosomes Each species has a characteristic chromosome number Mitosis and cytokinesis The diploid 2n number includes two sets of chromosomes of each type 0 Each type represented twice in each body cell diploid The haploid n number for humans is 23 During interphase a cell prepares for cell division Organelles are duplicated including centrosome At the end of S phase 0 Each chromosome is internally duplicated o Consists of two identical double helical DNA molecules Sister chromatids 2 strands of genetically identical chromosomes Attached together at a single point called the centromere 0 During mitosis Centromeres holding sister chromatids together separate Sister chromatids separate Each becomes a daughter chromosome Daughter chromosomes of each type distributed to opposite daughter nuclei 0 Just outside the nucleus is the centrosome This is the microtubule organizing center in animal cells Centrosome was also replicated in Sphase of interphase so there are 2 centrosomes before mitosis begins 0 In animals the centrosome contains two barrel shaped centrioles Centrosome organizes the mitotic spindle Cytokinesis in plant and animal cells 0 Cytokinesis division of cytoplasm Allocates the mother cell s cytoplasm equally to daughter cells Encloses each daughter cell in its own plasma membrane Often begins in anaphase Proceeds differently in plant and animal cells Animal cytokinesis Cleavage furrow appears between daughter nuclei Cytokinesis in plant cells begins with the formation of a cell plate Many small membrane bound vesicles are made by golgi The membrane of the cell plate become the plasma membrane between the daughter cells 00000 O The space between the daughter cells becomes lled with the middle lamella Functions of mitosis in animal and plant cells Functions of mitosis O O 0 It permits growth and repair ln owering plants meristematic tissue retains the ability to divide throughout the life of the plant Trees increase their width each growing season In mammals mitosis is necessary when A fertilized egg becomes an embryo An embryo becomes a fetus After birth as a child becomes an adult A cut that needs healing or broken bone mending Stem cells Many mammalian organs contain stem cells 0 They retain the ability to divide Red bone marrow stem cells divide to produce various types of blood cells Therapeutic cloning to produce human tissues can begin with either adult stem cells or embryonic stem cells Embryonic stem cells can be used for reproductive cloning the production of a new individual 94 The cell cycle and cancer Abnormal growth of cells is called a tumor 0 O Benign tumors are not cancerous Malignant tumors are cancerous Characteristics of cancer cells 0 O O O 0 Cells are nonspecialized Cells are immortal can enter the cell cycle repeatedly Form tumors Mitosis is normally controlled by contact with neighboring cells contact inhibition Undergo metastisis The original tumor easily fragments New tumors appear in other organs Undergo angiogenesis Forms new blood vessels Have abnormal nuclei 0 O 0 Cells may be enlarged Cells may have abnormal number of chromosomes Cells often have extra copies of genes Do not undergo apoptosis 0 Normally cells with damaged DNA undergo apoptosis o The immune system can also recognize abnormal cells and trigger apoptosis 0 Cancer cells are abnormal but fail to undergo apoptosis The origin of cancer Normal growth and tissue maintenance depends on a balance between signals that promote and inhibit cell division Two types of genes may be mutated when the balance is upset which may cause the cancer 0 Oncogenes Protooncogenes code for proteins which promote the cell cycle in various ways If a protooncogene id mutated it may become an oncogene 0 Tumor suppressor genes code for proteins which inhibit the cell cycle and promote apoptosis in various ways If a tumor suppressor gene becomes inactive it may promote cancer development 0 Both protooncogenes and tumor suppressor gene becomes inactive it may promote cancer development Both protooncogenes and tumor suppressor genes are normally regulated in coordination with organism s growth plan Other causes of cancer telomeres Chromosomes normally have special material at each end called telomeres These get shorter each cell division When they get very short the cell will no longer divide Telomerase is an enzyme that maintains the length of telomeres Mutations in telomerase gene 0 Cause telomeres to continue to length which allows cancer cells to continually divide 95 prokaryotic cell division The prokaryotic chromosome is a ring of DNA and a few associated proteins 0 Folded up in an area called the nucleoid Binary ssion o 2 replicate chromosomes are distributed to two daughter cells 0 Produces 2 daughter cells identical to original cell asexual reproduction o E coli has a generation time of about 20 minutes Comparing prokaryotes and eukaryotes Binary ssion and mitosis both ensure that the daughter cell is identical to the parent Prokaryotes protists and some fungi are single celled In multicellular fungi plants and animals cell division is important for growth renewal and repair No spindle is involved in binary ssion


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