DNA Replication Flashcards
What is DNA replication?
The process of creating an exact copy of a DNA molecule
Transcription - Copying a gene from DNA into mRNA
Translation - Creating protein from mRNA instructions
Replication stats
Occurs in the S stage of Interphase
New strand of DNA is created in the 5’ to 3’ direction
The template strand is read in the 3’ to 5’ direction
The process is called SEMICONSERVATIVE
Each new DNA molecule contains one stand of the original, complimentary DNA molecule and one new parent strand
What is the First step oF DNA replication?
DNA Helicase ~ Unwinds/Unzips DNA by breaking hydrogen bonds between nitrogenous bases
This creates two Y-shaped areas at each end of the unwound area
The initiation point where the splitting starts is called the ORIGIN OF REPLICATION
The structure that is created is called REPLICATION FORK
Replication takes place in several places simultaneously. Each REPLICATION BUBBLE represents two replication forks
moving in opposite directions along the length of the chromosome
As replication proceeds along the strand, the bubbles grow until they meet
What is the Second step of DNA replication?
RNA Primase ~ ( a short strand of RNA) must serve as the starting point for the attachment of new nucleotides
What is the Third step of DNA replication?
An enzyme, called DNA Polymerase inserts into the replication bubble and begins to add nucleotides that are complimentary to the existing strand
This is known as elongation
Nucleotides are only added 3’ end, never to the 5’ end
Thus, a daughter DNA strand can only grow in the 5’ - 3’ direction
One strand is replicated continuously from the 5’ - 3’ direction. This strand is known as the leading strand
The other strand, known as the lagging strand, is replicated in short segments known as Okazaki Fragments
What is the Fourth step of DNA replication?
The Okazaki Fragments are then spliced together by an enzyme called DNA Ligase
What is the Fifth step of DNA replication?
DNA Polymerase removes the RNA Primer
DNA Polymerase plays an important role in proofreading as well - it can tell when there is a mismatch in base pairing
and repair it
As soon as the newly formed strands are complete they rewind into the double helix structure
What is the Sixth step of DNA replication?
Termination ~ The completion of the new DNA strands and the dismantling of the replication machine
