Prokaryotic vs Eukaryotic Replication

StudyBlue printing of Prokaryotic vs Eukaryotic Replication html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, font, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td { margin: 0; padding: 0; border: 0; outline: 0; font-size: 100%; background: transparent; } body { line-height: 1; } blockquote, q { quotes: none; } blockquote:before, blockquote:after, q:before, q:after { content: ''; content: none; } /* remember to define focus styles! */ :focus { outline: 0; } /* remember to highlight inserts somehow! */ ins { text-decoration: none; } del { text-decoration: line-through; } /* tables still need 'cellspacing="0"' in the markup */ table { border-collapse: collapse; border-spacing: 0; } /* end RESET */ .header { min-width:800px; } .logo { padding:6px 20px 2px 20px; margin:0; font-size:25px; font-weight:bold; color:#808285; position:relative; border-bottom: 1px solid #c5c5c5; } .logo-blue { color:#70adc4; } .logo-desc { font-weight:normal; font-size:19px; color:#cccccc; margin-top:50px; position:absolute; display: none; } .back-button { position:absolute; top:20px; right:20px; font-size:13px; line-height:25px; color:rgb(0,175,225); font-weight:normal; } .back-button a { color:rgb(0,175,225); } .instructions { padding:0; margin:0; width:100%; position:relative; color:rgb(100,100,100); } .step-holder { border-left:1px solid #ededed; margin-left:20px; } .steps { padding:15px 0; float:left; width:24%; border-right:1px solid #ededed; text-align:center; } .steps-01 { } .steps-02 { } .steps-03 { } .steps-04 { } .label { padding:5px 10px; } .print-button { } .print-button a { background-color:rgb(0,175,225); color:white; line-height: 19px; padding:9px 8px 5px 30px; font-size:14px; text-decoration:none; background-image: url(images/printer.png); background-repeat: no-repeat; background-position: 7px 50%; -moz-border-radius: 5px; -webkit-border-radius: 5px; } .print-button a:hover { background-color:black; } .theNote .content { width: 8.0in !important; margin: 5px auto; padding:20px; background-color:white; } .theNote .header { border-bottom: 1px dashed #C8C8C8; font-size: 17px; padding: 0 0 10px; line-height: 19px; color: #00ADE1; min-width:500px; } .theNote .body { font-size: 14px; line-height: 19px; padding: 10px 0; } .theNote{ padding:6px 0; clear:both; background-color: rgb(200,200,200); } .theNote h3{ color: rgb(100,100,100); } .theNote h1, .theNote h3{ background-color:white; padding:2px 20px; width:8.0in !important; margin: 0 auto; font-size: 15px; } .theNote h1{ padding-top: 10px; font-size: 15px; } .theNote h1:first-child{ font-size: 20px; } .theNote h3 { font-size: 14px; font-weight: normal; } #options { border: 3px double #ccc; padding: 5px 12px; margin: 10px 50px 10px 20px; float: left; } #info { border-top: 1px solid #ccc; padding-top: 5px; font-style: italic; } li { margin: 5px 10px 5px 25px; } ul li { list-style: disc; } ol li { list-style: decimal; } img { border: 0; } table { clear: both; width: 100%; border: 1px solid #c5c5c5; border-width: 1px 0; margin: 0; page-break-after: always; } table#page { page-break-after: auto; } td { text-align: center; font-size: 12px; border-bottom: 1px dashed #c5c5c5; height: 1.75in; width: 50%; padding-left: 15px; } .leftside { border-right: 1px solid #cccccc; padding: 0 15px 0 0; } .bottom td { border-bottom: none; } .clearfix { clear:both; line-height:1px; height:1px; } img { max-width:80%; max-height:150px; margin:20px; } @media print {.header { display: none; } .content .header{ display:inherit; } table { border: 1px dashed #bbb; border-width: 1px 0; } .theNote{ background-color:white; } } null Biology 205 - Genetics I. Differences between eukaryotic and prokaryotic DNA replication. A. In eukaryotes the nucleosome structure must also be replicated. B. The Okazaki fragments are smaller (averaging 135 bases). C. Replication occurs only during the S phase of interphase. The cell cycle is regulated by cyclin-dependent kinases (Cdks) which function at the checkpoints. Cdks are enzymes which attach phosphate groups to other regulatory proteins. They are activated by cyclins. In prokaryotes, DNA replication occurs constantly . D. Except for a herpes virus DNA polymerase, eukaryotic DNA polymerases have no 5’ ® 3’ exonuclease activity. The FEN1 enzyme removes the primer. E. Replication is about ten-fold slower than in prokaryotes. F. Each chromosome has many origins of replication (ORIs). (See figure 11.12.) G. DNA polymerases are named with lower case Greek letters. About 15 are known, but we will only discuss 5: a, b, g, d and e 1. a , b , d and e are found in the nucleus. 2. g is found in the mitochondria. 3. Functions: a. α, δ and ε are responsible for nuclear DNA synthesis. The Pol α/primase is responsible for initiation. b. b is responsible for DNA repair. c. g replicates the mitochondrial DNA. H. 2 DNA ligases are involved: I and II. 1. DNA ligase I is found in proliferating cells. 2. DNA ligase II is found in resting cells. I. Chromatin and chromosome structure: 1. The “old” nucleosome disassembles into a H3-H4 tetramer (2 H3 and 2 H4) and two H2A-H2B dimers. The “old” H3-H4 tetramer gets transferred to one of the new DNA strands and a “new” tetramer binds the other new strand. Dimers are then added to complete the nucleosome. A nucleosome can thus consist of any combination of “new” or “old” tetramers with two “new” or two “old” dimers (or one of each). Histone chaperones help the nucleosomes form. 2. The protein scaffold to which the chromatin is anchored to make the chromosome contains a topoisomerase (presumably to release supercoils induced in each loop of chromatin during replication). J. Telomeres prevent loss of genetic material at chromosome ends. Replication of linear chromosomes would result in progressive shortening of lagging strands. Telomeres have multiple repeats of short sequences (TTAGGG in humans or TTGGGG in Tetrahymena ) which are added to the 3’ end of the DNA and serve as the template for the lagging strand to prevent shortening. See Figures 11.14 and 11.15. The telomerase RNA is used as a template to synthesize new telomere repeats. This is an example of reverse transcription , as the RNA is used to direct the synthesis of DNA, instead of the other way around. The RNA binds at the 3’ overhang and is then extends it. This process happens repeatedly, until there is enough 3’ overhang for a primer to be formed and another Okazaki fragment to be produced. II. A Comparison of DNA Replication in Prokaryotes and Eukaryotes PROPERTY PROKARYOTES EUKARYOTES 5’ to 3’ direction of synthesis + + Semiconservative + + Semidiscontinuous + + Size of Okazaki fragments 100 - 1000 bases 35 - 300 bases Number of ORIs 1 many (500 – 35,000) Bidirectional forks + + Primers RNA RNA Primer size 5-10 bases 10 bases RNA + 30 bases DNA Polymerases I, II, III, IV, V (III = dimer) a , b , g , d , e (no dimers) + 3’ to 5’ proofreading All 3 polymerases g , d , e 5’ to 3’ exonuclease Only polymerase I FEN1 Helicases + + SSBs + + DNA ligase I I, II Topoisomerases + + Telomerase - + Initiator protein DnaA origin recognition complex (ORC)