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.

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