Central Dogma: DNA Structure and Replication Flashcards
Where does DNA replication take place?
Nucleus
What does Gene Regulation show?
Gene regulation shows that you can alter the amount of RNA produced by genes coded on the DNA.
The amount of RNA can then dictate the amount of protein and therefore how much a particular reaction happens in the cell
What are the three main molecules of function in the central dogma
DNA, RNA and Proteins
DNA with its double helix stores information
RNA is less stable and single stranded transfers information
Proteins with huge variety and 3D shape execute functions
Why a double stranded molecule?
Two complementary strands that can act as templates
The second strand can serve as a template for the repair of a damaged strand
The double helix provides a chemically stable environment in which to store the genetic information
Outline Phosphodiester bonds formed by DNA Ligase
Ligase repairs the DNA back bone and is used to join two molecules of DNA together
(DNA polymerase needs a template strand so cannot do this)
Outline DNA replication
DNA replication initiates at specific points called origins, where the DNA double helix is unwound
Short segment of RNA called a primer is synthesized and acts as a starting point for new DNA synthesis
An enzyme called DNA polymerase next begins replicating the DNA by matching bases to the original strand
Once synthesis is complete, RNA primers replaces with DNA and gaps between newly synthesized DNA segments are sealed together with enzymes
Outline the Leading strand
On the leading strand DNA replication proceeds continuously along the DNA molecule as the parent double-stranded DNA is unwound
Outline the lagging strand
On the lagging strand the new DNA is made in instalments which a re later joined together by a DNA ligase enzyme
Lagging strand DNA replication in EUKARYOTES
RNA primers are made at intervals of about 200 nucleotides on the lagging strand, each RNA primer of approx. 10 nucleotides long
Primers are removed
The gaps are filled in by a repair DNA Polymerase
Completed fragments are finally joined together by an enzyme called DNA ligase
RNA primers are synthesised by an RNA Polymerase called primase which uses a DNA strand as a template
Primase works 5’ to 3’
Primase can do something dna polymerase cannot, it can start a new polynucleotide chain by joining together two nucleotides triphosphates without the need for base paired 3’ end as a starting point
Outline the group of proteins that act together as a replication machine
DNA polymerase are held on the leading and lagging strands by circular protein clamps, allowing the polymerases to slide
On the lagging strand template, the clamp detaches each time the polymerase completes an Okazaki fragment . A clamp loader is required to attach a sliding clamp each time a new Okazaki fragment is begun
At the head of the fork DNA helicase unwinds the strands of the parental DNA double helix. Single stranded DNA - binding proteins keep the DNA strands apart to provide access for the primase and polymerase
