Mitosis and Meiosis
Mitosis and Meiosis 40763 - BMS 110 - B
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This 8 page Class Notes was uploaded by tess2019 on Thursday October 8, 2015. The Class Notes belongs to 40763 - BMS 110 - B at Missouri State University taught by Ivy J Fitzgerald in Fall 2015. Since its upload, it has received 13 views. For similar materials see Introduction to the Biomedical Sciences in Biomedical Sciences at Missouri State University.
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Date Created: 10/08/15
Mitosis and Meiosis Monday September 21 2015 1239 PM Mitosis duplicate cell to make two identical daughter cells Meiosis divide cell to be ready to make babies by sexual reproduction Chromosomes Humans have 46 chromosomes 0 23 pairs within a cell39s nucleus one from each parent 0 Pairs of chromosomes homologous chromosomes Autosomes 0 Pairs 122 0 Control traits that do not relate to gender of an individual 0 Sex chromosomes 0 1 pair that contains the genes for controlling gender 0 XX in females and XY in males Diploid 2nfull number of chromosomes body somatic cells contain 46 chromosomes Haploid n half the number of chromosomes sex cells gametes contain 23 chromosomes Terminology Genesegment of DNA in a chromosomethat encodes a protein Chromatin DNA packaged with protein Chromosomecoiledcondensed DNA and protein Sisterchromatids chromosome and its copyidentical fused until division Centromere region of DNA on chromosome where microtubules attach Kinetochore protein complex at centromere where microtubules attach Centriole microtubule origin Centrosome centriole surrounding proteins Mitosis Division of somatic cells 0 Growth 0 Replacement ofdead cells 0 Tissue repair 0 Developing embryo and fetus 0 Cell divide to make whole body 0 Children 0 Cells divide for growth and repair 0 Adults 0 Some cells lose ability to divide most neurons 0 Some cells stop dividing but maintain the ability to divide if needed liver cells 0 Some cells actively divide throughout life skin cells The Cell Cycle Cell cycle quotlifetimequot of a somatic cell varies depending on cell type lnterphase o 61 first quotgapquot cell growth 0 5 DNA copied duplicated chromosomes called chromatids attached at centromere o Gz second quotgapquot preparation for mitosis more growth 0 M mitosis o Mitosis chromosomes sorted into two sets and the cytoplasm divides four phases 0 Cytokinesis separation of daughter cells lnterphase G1 phase growing 5 phase synthesis 0 Before mitosis can begin the DNA must be replicated DNA replicated duringS phase of interphase 0 The sister chromatids are held together at the centromere a densely packed region of chromatin 62 phase more growth Mitosis Prophase First step of mitosis Chromatin condenses to form chromosomes Nucleolus disappears Centrosomes are duplicated and move toward opposite poles Microtubules form Prometa phase 0 Nuclear envelope breaks down and disappears Kinetochores form at centrome res on sister chromatids Microtubules attach to kinetochores Meta phase Duplicated chromosomes aign midway between the poles ofthe ce Line up in the center at the metaphase plate 0 One sister ch romatid is attached to a microtubule from one pole the other sister ch romatid to the microtubule from the other poe Thought that cells can feel the tension of the ch romatid pairs attached to both spindle poles Takes half the time of mitosis Ana phase Once sister chromatins are properly aligned at the metaphase plate the cohesin rings that hold the sister ch romatids together are cleaved Sister ch romatids split and become independent chromosomes 0 Chromosomes pulled by the microtubules toward the pole region 0 Spindle elongates pushing the poles father apart Telophase Chromosomes no longer connected to the microtubule spindle Chromosomes unpack from the chromosome state to looser chromatin structure threadlike 0 Nuclear envelope reforms 0 End of mitosis Cytokinesis Cytokinesis division of the cytoplasm cytosol and organelles yr Begins toward the end ofthe anaphase 0 Goes on concurrently with anaphase and telophase Cleavage Furrow 0 Formsin late anaphase 0 Microfilaments actin pull the plasma membrane inward all around the cell microfilaments form a ring 0 Pinches the cell in two lnterphase Prophase Prometaphase Metaphase An aphase Tnlnnhaon n 46 Chm mo somes Chromosomes doubled to 92 Nucleus dissolves and microtubules attach to centromeres Chromosomes align at middle of cell Separated chromosomes pulled apart Micro tubules disappear I CIUPIIGDC 39 f 52 cell division begins gt 2 Two daughtercells formed CYtOKmes39s gt gt 8 l gt lt lt each with 46 chromosomes J J BA Eduauion Anaphase A Kmetochore Aster microtubules Motor protein Centnoles Kinetoch ore I microtuoule Tubulin subunit lost due Spindle to depolymenzation pole Centrosome Polar greughte microtubules Toma I Spindles lengthen microtubules separate sister ch romatids in anaphase Meiosis Meiosisthe process by which gametes are formed 0 Gamete haploid cell for fusion with a gamete from the opposite sex during sexual reproduction o Produced by gametogenesis 0 Male gamete sperm or spermatozoon produced by spermatogenesis 0 Female gamete egg or oocyte produced by oogenesis 0 Meiosis happens in a specific location in the body 0 Male testes 0 Female ovaries 0 Sometimes considered quotdouble meiosisquot 0 Each final cell has one copy of each chromosome haploid o Humans 23 chromosomes 1 of each kind Homologous recombination occurs to mix genes Produces4 haploid cells Chromosomes Homologous chromosomes contain the same genes 0 Though may contain differentforms of the gene alleles Same allele from both mom and dad Interphase Similar to mitotic interphase First DNA is replicated during S phase 0 The sister chromatids are held together at the centromere a densely packed region of chromatin Meiosis Divides homologous chromosomes Prophasel Homologous chromosomes pair synapsis Longest phase of meiosis 90 ofthe time Homologous recombination quotcrossing overquot 0 Portions of a chromosome can be swapped with the homologous region from a different chromosome 0 Chiasma singular chiasmata plural point of crossover 39 Humans average just over 2 chiasmata per tetrad Late Prophasel 0 Nuclear envelope breaks down 0 Chromosomes become attached to spindle fibers microtubules 0 Similar to mitotic prophase Metaphase The pairs of homologous chromosomes align midway between the poles ofthe cell metaphase plate Homologous chromosomes remain paired up at metaphase plate Ana phase I Homologous chromosomes separate and move to opposite poles Telophase Chromosome movement is finished and nuclear envelope reforms Cell uses cytokinesis to divide and complete daughter cells 0 Cleavage furrow divides the plasma membrane 0 Same timing as mitosis NOTHING HAPPENS BETWEEN TELOPHASE I AND MEIOSIS Meiosis Divides sister ch romatids Prophasell Sister chromatids in each cell condense and attach to spindle fibers Metaphase Sister ch romatids move to the center ofthe cell metaphase plate Anaphase Sister ch romatids disjoin and move to opposite poles ofthe cell Telophase Chromosomes unpack and new nuclear envelopes begin to form Cytokinesis divides cytoplasm to separate and form new daughter cells Daughter cells are all different Interphase gt 46 Chromosomes Chromosomes double to 92 o x Prophase a 5 quot l and crossover x a X gt xx Nucleus dissolves and Prometaphase L V 1 x 1 microtubules attach to x centrumeres x 2 Chromosomes align Metaphase 1 l 39239 j at middle ofcell Anaphase 1 Telophase 1 interphase 2 Metaphase 2 Anaphase 2 Separated chromosomes pulled apart Micro tubules disappear cell division begins Two cells formed each with 46 chromosomes Micro tubules attach to cen tromeres Chromosomes pulled apart to 28 Microtubules disappear cell division begins 4 cells formed each with 23 chromosomes