How Cells Divide (10.1-10.3)
How Cells Divide (10.1-10.3) BIOL 201L 004
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BIOL 201L 004
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This 5 page Class Notes was uploaded by Feben Notetaker on Friday October 9, 2015. The Class Notes belongs to BIOL 201L 004 at Towson University taught by Dr. Sarah Texel in Fall 2015. Since its upload, it has received 29 views. For similar materials see Introduction to Cell Biology and Genetics in Biology at Towson University.
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Date Created: 10/09/15
Section 101 Bacterial Cell Division Friday October 9 2015 254 AM Bacteria divide to reproduce They exchange DNA but don39t have a sex cycle Bacterial division is clonal o All genetic material between offspring and ancestor is identical I Unlessthere is error in genetic coding Basic process of cell division 0 Duplication o Segregation of genetic info into daughter cells 0 Division of cellular contents BINARY DIVISION Bacterial DNA is circular and 500 times bigger than the cell 0 Verytightly packed 0 Located in the nucleoid Proteins called the structural maintenance of chromosome SIVI C aid in the organization and compaction of the nucleoid 0 Have diversified to serve different functions I EX are cohesin and condensin proteins in eukaryotes Chromosome divides then cell divides 1 Replication of circular DNA begins at the origin of replication 2 Enzymes move out in both directions duplicating DNA till it reaches its quotend pointquot also known as terminus of replication 3 DNA elongates and Original and Duplicate DNA start to divide a Their terminus of replication are both facing the middle of the cell 4 Septation occurs asa cell wall and membrane begin to grow at midpoint of cell while being aided by FtsZ a FtsZ a protein that aids in Septation i Found in prokaryotes and archaea ii Formsfilaments and rings iii 3D crystals similar to eukaryotic tubulin iv Has a diff role in bacterial division than mitosis in eukaryotes 5 When Septation finishes the cell pinches in two and becomestwo separate cells Segregation of chromosome is alwaysthe movement of origin fist then the duplication moves to the other end as nucleoid forms Septum partition between the membrane of the original and replicated cell Septation process of making a septum o Occurs in the middle of the cell c Begins with the formation of a ring How Cells Divide Page 1 o composed of multiple copies of FtsZ I Proteins are created proteins embedded in membrane rtigtn of r Eellwalt reptnatiion Ehr m eme Two wigs mpt ieatinn of tartan thEttns Replication Edn nues Replication finishes a Two tie uhtEzr teats result I E J 11 I Ml F httpwwwquiacomfiesquiausersImcqeemitosisAP Chapter 12binary fissionin How Cells Divide Page 2 Section 102 Eukaryotic Chromosomes Friday October 9 2015 352 AM Walter Flemming 1879 discovered mitosis in salamander larvae through a primitive light microscope 0 Saw minute threads with in the nuclei that appeared to be dividing length wise Mitosis asexual division between cellsthat involve DNA replication and nuclear and cell division Chromosomes are found in all eukaryotes o of chromosomes vary bw species rangesfrom 1500 pairs 0 Eukaryotes have between 1050 pairs in their body cells Human cells have 46 chromosomes and has 23 identical pairs 0 Each chromosome has hundreds to thousands of gene that determine function and development M onosomy embryos missing one chromosome Trisomy extra copy of chromosome 0 Not fatal when smallest chromosomes are involved Chromatin acomplex of DNA and protein Make up chromosomes M ost chromosomes are 40 DNA and 60 protein Chromosomes are the sites of RNA synthesis Each chromosome has a single DNA molecule that runsthrough the entire chromosome39s length Atypical human chromosome has about 140 million nucleotides A strand of DNA laid out from a single chromosome is about 50m 2quot long 0 DNA is compacted in the cell Heterochromatin unexpressed domain of chromatin Euchromatin expressed domain of chromatin DNA in a eukaryotic nucleus under an electron microscope resembles a string of beads Histone proteins positively charged proteins that DNA coils around 0 Attracts negative charge of phosphate groups in DNA 0 Guides coiling of DNA Nucleosome complex of DNA and histone proteins DNA histone DNA in nucleosome is coiled into a more compact structure called solenoid Look Figure 105 p190 During mitosis a scaffold of protein come together that helps compact chromosomes that can be readily separated Compaction is modeled by looping of chromatin fibers like awire brush 0 Condensin aidsthe compaction to be formed Karyotype array of chromosomes an individual organism possesses of chromosomes in a species are counted by the of haploids Haploid n set necessary to define an organism Diploid 2n total number of chromosomes in acell o Twice the haploid number 0 Reflects equal genetic contribution from parents Humans haploid 23 diploid 46 Homologous maternal and paternal chromosomes Homologue each parent39s haploid Cohesins protein that holdsthe two identical chromosomestogether Sister chromatids two identical chromosome strands combined at the center by the centromere Products of replication being held together is critical to division process Cell must ensure that the offspring receives a complete set of chromosomes Instead of labeling chromosomes cells glues replication products at the centromere o Mitosis separates these copies at the same time to make sure the offspring get a copy of each chromosome How Cells Divide Page 3 http4bpbloqspotcom0hW1wquhc8 UyP xA8Lm QPI AAAAAAAACvM 9g06 EBexED st 60 0 HumanChromosomesipq bmma s Hrumlugmm Ehrzi mumm Eemmmeme Evaplatinum 1 SETH Sister Chi mti i fhn i i l l l id httpgtatic1 guaremceeomgtatic5240dde2e4b00424461203e1t5254b085e4b0a34313 Oce8021381281926054homoloqous chromosomesipq How Cells Divide Page 4 Section 103 Overview of Eukaryotic Cell Cycle Friday October 9 2015 444 AM Cell Cycle requires the duplication of the genome accurate segregation and division of cellular contents CELL CYCLE PHASES G1 Gap Phase 1 the primary growth phase of a cell 0 Fills gap bw cytokinesis and DNA synthesis 0 Longest phase GOphase some cells pause before replication and remain there for daysto years before moving on to cell division 0 EX muscle and nerve cells remain in G0 phase permanently O EX lJver cells resume to G1 phase in response due to factors released during injury SSynthesis the cell synthesizes a replica of the genome G2 Gap phase 2 the second growth phase 0 Preparation for separation for newly replicated genome o Fills gap bw DNA synthesis and beginning of mitosis o Microtubules reorganize to form aspindle Interphase Phases G1 through G2 bw cell divisions Mitosis phase of the cell cycle in which 0 Apparatus assembles O Binds to chromosomes 0 M oves sister chrom atids apart 0 Essential separation of two daughter cells 0 Five stages I Prophase I prometaphase I Metaphase I Anaphase I TeIOphase httpsuploadwikimediaorqwikipediacommonsth Cytoklnesls phase of the cell cycle when cytoplasm dIVIdes making two daughter cells umbeeoCe mole 22SVq20000XCe Cycle M phase combo of mitosis and cytokinesis phase 22svgpng Duration of cell cycle varies 0 Cells in animal embryos complete cell cycles in under 20min 0 Shortest animal nuclear division cycle is in the fruit fly embryo 8min O M ature cellstake a longer time to grow I Longer than embryonic tissue 0 M ammalian cells usually takes 24hrs to complete cell cycle 0 lJver cells can take up to one year 0 M phase is one of the shorter phases How Cells Divide Page 5