DNA Replication PDF
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Summary
This document details the process of DNA replication. It explains the different models of DNA replication, including the semi-conservative model, and describes the enzymes and proteins involved in the process. The document also covers the replication fork and Okazaki fragments.
Full Transcript
DNA REPLICATION DNA replication: is the process by which the genetic material is copied prior to distribution into daughter cells or the process of copying a parental DNA molecule to form two daughter DNA molecules. Process of DNA replication is Semi Conservative process S...
DNA REPLICATION DNA replication: is the process by which the genetic material is copied prior to distribution into daughter cells or the process of copying a parental DNA molecule to form two daughter DNA molecules. Process of DNA replication is Semi Conservative process Semi conservative model Parent molecule Daughter DNA molecules ❑ DNA replication begins at specific locations, or origins of replication, in the genome. ❑ Unwinding of DNA at the origin and synthesis of new strands results in replication forks. ❑ Bacterial chromosomes have a single origin of DNA replication. ❑ Eukaryotic chromosomes contain multiple origins of Replication. proteins that associated with the replication fork which helps in initiation and continuation of the replication process. ❑ DNA helicases ❑ SSBS (Single-strand DNA binding proteins) ❑ Topoisomerases ❑ RNA primase ❑ DNA Polymerases ❑ Sliding DNA clamps ❑ Rnase H ❑ DNA ligase شوكة التناسخ THE REPLICATION FORK يتم تناسخ سلسلتي الـ DNAمعا ً عند شوكة التناسخ. Both Strands of DNA Are Synthesized Together at the Replication Fork Leading strand Lagging strand تتفاوت شظايا أوكازاكي في الطول من 1000إلي 2000نيكلوتيدة في البكتيريا ومن 100إلي 400نيكلوتيدة في حقيقيات األنوية بدء نسخ أى سلسلة جديدة من الـ DNAيتاطلب بادئ من الـ RNA The Initiation of a New Strand of DNA Requires an RNA Primer ❑ الـDNA Helicases الحلزوني اللولب بفك المزدوج للـDNA قبل Processivity شوكة التناسخ ❑ DNA Helicases Unwind the Double Polarity Helix in Advance of the Replication Fork. ❑ It is ring shaped hexamers proteins. Single-Stranded Binding Proteins Stabilize Single-Stranded DNA Prior to Replication Topoisomerases Remove Super coils Produced by DNA Unwinding at the Replication Fork RNA primer 3’-OH 3’-OH للبادئ المكون بفعل ) (3’-OHللنهاية )(DNA polymerase IIIيتم إضافة النيكلوتيدات بفعل إنزيم الـ .يخرج مجموعتين من الفوسفات مع إضافة كل نيكلوتيدة ثالثية الفوسفات RNA Primaseإنزيم الـ وتستغل الطاقة الناتجة لتنشيط تفاعل االستطالة. Sliding DNA clamps A protein which prevents DNA polymerase III from dissociating from the DNA parent strand. Sliding DNA clamp increase processivity of DNA polymerase. يجب إزالة مناطق RNA Primers الـ إلكمال تناسخ DNA الحامض النووي RNA Primers Must Be Removed to complete DNA replication DNA Synthesis is Semidiscontinuous ❑ Leading strand: the DNA daughter strand synthesized continuously ❑ Lagging strand: the DNA daughter strand synthesized discontinuously ❑ Okazaki fragments: short pieces of DNA at the replication fork. Okazaki fragments are 1000-2000 nucleotides long in Prokaryotes, and 100-200 nucleotides long in Eukaryotes.