Ch 12 Cell Cycle BIO1300 PDF

Ch. 12 The Cell Cycle Continuity of life is based on the reproduction of cells, or cell division – In unicellular organisms, division of one cell reproduces the entire organism – Multicellular organisms depend on cell division for – Develo...

Ch. 12 The Cell Cycle Continuity of life is based on the reproduction of cells, or cell division – In unicellular organisms, division of one cell reproduces the entire organism – Multicellular organisms depend on cell division for – Development from a fertilized cell (a zygote) – Growth & Repair throughout their lifetime Video Online to Watch Searchable on Youtube.com “Cell Division & Cell Cycle” Run time 5:34 min by Frank Gregorio Feb 2010 © 2011 Pearson Education, Inc. Concept 12.1: Most cell division results in genetically identical daughter cells Most cell division (called Mitosis) results in daughter cells with identical genetic information, DNA – Exception is meiosis, special type of division to produce sperm and egg cells All the DNA in a cell constitutes the cell’s genome – A genome consists of a single DNA molecule (prokaryotic cells) or a number of DNA molecules (eukaryotic cells) – DNA molecules in a cell are packaged into chromosomes – Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus Somatic cells (nonreproductive cells) have 2 sets of chromosomes Gametes (reproductive cells: sperm & eggs) have half as many chromosomes as somatic cells, so only 1 set of chromosomes © 2011 Pearson Education, Inc. Distribution of Chromosomes During Eukaryotic Cell Division In preparation for cell division, DNA is replicated and the chromosomes condense Each duplicated chromosome has two sister chromatids (joined copies of the original chromosome), which separate during cell division – Centromere is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached Fig. 12.4 © 2011 Pearson Education, Inc. Fig. 12.5 During cell division (mitosis), the 2 sister chromatids of each duplicated chromosome separate & move into 2 nuclei Once separate, the chromatids are called chromosomes © 2011 Pearson Education, Inc.  INTERPHASE S G1 (DNA synthesis) Meaning Chromosomes Duplicated Here s is e k in G2 s is t o Cy to MIT Mi (M) OTI PH A C SE Fig. 12.6 The Cell Cycle: Cell division (mitosis) is an integral part of the cell cycle, the life of a cell from formation to its own division Concept 12.2: The mitotic phase alternates with interphase in the cell cycle The cell cycle consists of Mitotic (M) phase (mitosis and cytokinesis) Interphase (cell growth and copying of chromosomes in preparation for cell division) – Interphase (about 90% of the cell cycle) can be divided into 3 subphases – G1 phase (“first gap”) – S phase (“synthesis”) – G2 phase (“second gap”) The cell grows during all 3 phases of interphase, but chromosomes are duplicated only during the S phase © 2011 Pearson Education, Inc. Eukaryotic cell division consists of: Mitosis: division of the genetic material in the nucleus, divided into 5 phases and Cytokinesis: the division of the cytoplasm © 2011 Pearson Education, Inc.  P2MAT….the 5 stages of MITOSIS Youtube (runtime 1:30min Oct 2009):“A GREAT Mitosis Video” by Wesley McCammon http://www.bing.com/videos/search?q=mitosis+video&FORM=VIRE3#view= detail&mid=01E7175BBD52DE31CBD201E7175BBD52DE31CBD2 Fig. 12.7 Mitosis in Animal Cell G2 interphase…Prophase…Prometaphase…Metaphase…Anaphase..Telophase/Cytokinesis See the nuclear envelope break down before metaphase……then it reforms @ telophase Yellow are the centrosomes & the mitotic spindle, and the DNA is stained blue/purple. The Mitotic Spindle: A Closer Look The spindle is a structure made of microtubules that controls chromosome movement during mitosis Mitotic Spindle = Centrosomes + Spindle Microtubules + Asters In animal cells, assembly of spindle microtubules begins in the centrosome, the microtubule organizing center – Centrosome replicates during interphase, forming 2 centrosomes that migrate to opposite ends of the cell during prophase and prometaphase – During prometaphase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes – Each centrosome consists of 2 centrioles – Each centriole is a cylindrical array of 9 microtubles Centrosome Centromere: narrow “waist” of duplicated chromosome, where 2 chromatids are attached © 2011 Pearson Education, Inc. Fig. 12.8 THE MITOTIC SPRINDLE Aster (a radial array of short microtubules) extends from Centrosome each Centrosome (the Aster Metaphase microtubule organizing center) Sister plate chromatids (imaginary) Microtubules Chromosomes Kineto- chores Centrosome 1 µm Overlapping nonkinetochore microtubules Kinetochore microtubules At metaphase, the chromosomes Kinetochores are protein are all lined up at the metaphase complexes associated 0.5 µm plate, an imaginary structure at the with centromeres (the midway point between the spindle’s waist of the chromosome) two poles Mitosis Continued In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell – Microtubules shorten – Nonkinetochore microtubules from opposite poles overlap & push against each other, elongating the cell In telophase, genetically identical daughter nuclei form at opposite ends of the cell Cytokinesis begins during anaphase or telophase and the spindle eventually disassembles © 2011 Pearson Education, Inc.  Cytokinesis: A Closer Look In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow In plant cells, a cell plate forms during cytokinesis – Vesicles form cell plate that then forms new cell wall © 2011 Pearson Education, Inc. Fig. 12.10 Fill in the MITOTIC Diagram  BIO 1300 Schedule Mon 11/21 Submit at home photosynthesis lab 11am lecture in lab Ch. 12 & 13 Pickup graded draft lab reports Tue 11/22 Lecture Ch. 13 Th/F 11/24-25 Holiday Mon 11/28 No lab, work on final lab report Tues 11/29 Lecture Ch. 16 Fri 12/2 Lecture Ch. 16 Mon 12/5 Lab “Mitosis/Meiosis” Submit final lab report T/F 12/6 & 12/9 Lecture Ch. 17 Mon 12/12 Last Lab “DNA Isolation” Tues 12/13 Lecture Ch. 17 Wed 12/14 Mastering homework due Fri 12/16 Exam #2 (Ch.5,12,13,16,17) © 2011 Pearson Education, Inc. Since prokaryotes evolved Binary Fission in Bacteria before eukaryotes, mitosis probably evolved from binary fission Prokaryotes (bacteria & archaea) reproduce asexually by a cell division called Binary Fission: Chromosome replicates (beginning @ origin of replication) & 2 daughter chromosomes actively move apart Plasma membrane pinches inward, dividing cell into 2 Fig. 12.12 © 2011 Pearson Education, Inc. Concept 12.3: Eukaryotic cell cycle is regulated by a molecular control system Frequency of cell division varies by cell type Cell cycle driven by specific chemical signals present in cytoplasm & regulated by both internal & external controls – External signals are growth factors, proteins released by certain cells that stimulate other cells to divide Sequential events of the cell cycle are directed by a distinct cell cycle control system …. “a clock” Clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received For many cells, the G1 checkpoint is the most important © 2011 Pearson Education, Inc. Control of Cell Cycle If a cell receives a go- ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divide If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G0 phase Fig. 12.15 Loss of Cell Cycle Controls in Cancer Cells Cancer cells manage to escape usual cell cycle controls Cancer cells may not need growth factors to grow/divide as they may make their own growth factor & may have an abnormal cell cycle control system A normal cell is converted to a cancerous cell by a process called transformation – Cancer cells that are not eliminated by the immune system form tumors, masses of abnormal cells within otherwise normal tissue If abnormal cells remain only @ original site, lump is called a benign tumor Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors Recent advances in understanding cell cycle and cell cycle signaling have led to advances in cancer treatment © 2011 Pearson Education, Inc. Sarcomas = tumors from cells in connective tissue, bone or muscle Carcinomas = tumors from cells in epithelial tissue such as skin or lining the lung The constant cell division in epithelia seems to make these cells prone to genetic mutations, leading to abnormal growth patterns such as cancer or benign tumors. Some 90% or more of all cancers in adults over age 45 arise in epithelial tissues. Cancer…. a corrupt cell cycle. In the USA, the four deadliest cancers are lung, colon, breast & leukemia/lymphomas Source: Vodopich & Moore (2014) Lab Manual, Exercise 14 The p53 gene is a tumor-suppressor gene Because the p53 gene is nonfunctional in cancer cells, cancer cells repeatedly undergo cell division without being halted at the G1 checkpoint of the cell cycle Source: Vodopich & Moore (2014) Lab Manual, Exercise 14