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DNA Replication PowerPoint Presentation

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Description : Check out this medical titled "DNA Replication”.

This medical is about DNA replication, the process by which a cell copies its DNA prior to cell division. It is essential for the transmission of genetic information from one generation of cells to the next. During replication, the double-stranded DNA molecule unwinds and separates into two single strands, each of which serves as a template for the synthesis of a new complementary strand.

The replication process is catalyzed by a group of enzymes, including DNA polymerase, helicase, and primase. The helicase enzyme unwinds the double helix, while primase synthesizes a short RNA primer that is used as a starting point for DNA polymerase to begin synthesizing the new strand. DNA polymerase adds nucleotides to the growing strand in a 5 to 3 direction, using the existing strand as a template.

Replication proceeds in both directions from the origin of replication, resulting in the formation of two replication forks. As each fork advances, it creates a new strand of DNA in a continuous manner on one side (leading strand) and in a discontinuous manner on the other side (lagging strand) due to the antiparallel nature of DNA. This discontinuous strand is synthesized in short segments called Okazaki fragments, which are later joined by DNA ligase.

The accuracy of DNA replication is maintained by a number of proofreading mechanisms, including exonucleases that remove incorrectly paired nucleotides and DNA polymerases ability to recognize and correct mismatches. Errors that do occur can result in mutations, which can have important consequences for the cell and the organism as a whole.

Tags : DNA Replication, DNA polymerase, helicase, primase, helicase enzyme, Medical Genetics, Medical Genetics

Published on : Jun 01, 2023 | Views : 619 | Downloads : 6

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Slide 1-

2007-2008 DNA Replication Ch.12.2
Slide 2-

DNA Replication Purpose: cells need to make a copy of DNA before dividing so each daughter cell has a complete copy of genetic information 3 proposed Models of Replication
Slide 3-

Meselson and Stahl Experiment
Slide 4-

Semi-Conservative Model Replication of DNA base pairing allows each strand to serve as a template for a new strand new strand is 1/2 parent template & 1/2 new DNA
Slide 5-

Anti-parallel strands Nucleotides in DNA backbone are bonded from phosphate to sugar between 3 & 5 carbons DNA molecule has “direction” complementary strand runs in opposite direction THIS WILL CAUSE A PROBLEM FOR REPLICATION 3 5 5 3
Slide 6-

Bonding in DNA ….strong or weak bonds? How do the bonds fit the mechanism for copying DNA? 3 5 3 5
Slide 7-

DNA Replication Large team of enzymes coordinates replication
Slide 8-

Replication: 1st step Unwind DNA helicase enzyme unwinds part of DNA helix stabilized by single-stranded binding proteins PREVENTS DNA MOLECULE FROM CLOSING! DNA gyrase Enzyme that prevents tangling upstream from the replication fork single-stranded binding proteins replication fork helicase gyrase
Slide 9-

Replication: 2nd step RNA Primase Adds small section of RNA (RNA primer) to the 3’ end of template DNA Why must this be done? DNA polymerase 3 (enzyme that builds new DNA strand) can only add nucleotides to existing strands of DNA
Slide 10-

DNA Polymerase III Replication: 3rd step Build daughter DNA strand add new complementary bases With the help of the enzyme DNA polymerase III
Slide 11-

Replication: 4th step Replacement of RNA primer by DNA Done by DNA polymerase I
Slide 12-

Limits of DNA polymerase III can only build onto 3 end of an existing DNA strand Leading & Lagging strands Leading strand Lagging strand Okazaki fragments Okazaki Leading strand continuous synthesis Lagging strand Okazaki fragments joined by ligase “spot welder” enzyme DNA polymerase III   growing replication fork
Slide 13-

RNA primer is added built by primase serves as starter sequence for DNA polymerase III HOWEVER short segments called Okazaki fragments are made because it can only go in a 5 3 direction DNA replication on the lagging strand growing replication fork primase RNA
Slide 14-

NEXT DNA polymerase I removes sections of RNA primer and replaces with DNA nucleotides STRANDS ARE GLUED TOGETHER BY DNA LIGASE Replacing RNA primers with DNA growing replication fork DNA polymerase I RNA
Slide 15-

Replication fork 3’ 5’ 3’ 5’ 5’ 3’ 3’ 5’ helicase SSB = single-stranded binding proteins primase DNA polymerase III DNA polymerase III DNA polymerase I ligase Okazaki fragments leading strand lagging strand SSB