ZOL 141 1st Edition Lecture 5Outline of Last Lecture I. The CellII. OrganellesIII. Problems with Organellesa. ExamplesOutline of Current Lecture I. CELL CYCLEa. Interphaseb. Mitosisc. CytokinesisII. Mitosis is Essential to growthIII. Genetic Diseases Associated with problems of cell divisionCurrent LectureCELL CYCLEDefinition: sequence from one cell division to the next cell divisionThree stages:1. Interphase (G1, S, G2)2. Mitosis: produces two genetically identical daughter cells i.e.: nuclear divisiona. Telophaseb. Anaphasec. Metaphased. prophase3. Cytokinesis: cytoplasmic cell divisionDuplication and distribution of all materials- Time between divisions: varies from minutes to months or even years- Some cells stop dividing (such as cardiac cells)- Assume duplication once per dayInterphase G1- G1 (Gap 1): growth, i.e. organellses, membranes, ribosomes made, cell increases in size- Time frame: several hours (9-10)- Chromosome: One chromatidS (synthesis)- DNA is synthesized, chromosomes are duplicated- Time frame: several hours (9-10)- Chromosomes: two sister chromatidsG2 (Gap 2)- Preparation for cell division- Time frame: shorter than G1 and S (4 hours)- Chromosome: two sister chromatids- Mitochondria start to grow and divide- Spindle fibers begin to assembleMitosis: form of cell division that produces two genetically identical cells, Chromosomes have already replicated- Early prophase: two pairs of centrioles, nuclear envelope begins to break down, nuclear envelope starts to open up- Late prophase: chromosomes condense even more, centrioles migrate to top andbottom of cell- Transition to Metaphase: no nucleus, DNA dispersed throughout cell, spindle fibers begin to attach to centrioles with microtubules- Metaphase: chromosomes line up in middle of cell (equator), each chromosome connected to centriole- Anaphase: movement of chromosomes toward different poles, each chromatid separated, sister chromatids move to opposite poles, ensures that two daughter cells are genetically identical- Telophase: Nucleus begins to form again (in each daughter cell), still connected- Cytokinesis: Daughter cells completely divide from each otherMitosis is Essential for Growth- Cells which constantly divide: bone marrow (produces blood cells), skin cells- Cells which do not normally divide: cardiac muscle cells- Cells can divide about 50 times (Hayflick limit)- Adult cells: 10-30 times- Embryonic stem cells: unlimitedGenetic Diseases Associated with problems of cell division- Progeriao 1 in 4 million newborno normally new mutationo mutation in gene (LMNA) responsible for shape of nucleuso affects cell division; cells die prematurelyo affected individuals die on average by age 13 by hearth attack or stroke- Werner Syndromeo 1 in 200000 live birtho mutation in WRN geneo rapid aging, no growth spurt in puberty- Roberts Syndromeo Most severeo Problems with splitting of centromeres, chromosomes do not line up properlyo Symptoms: short arms and legs, facial abnormalities, deformations, mental impairment possibleo Very rare: only about 150 individuals known to have had