Molecular Genetics - DNA Synthesis Flashcards
DNA replication happens in this fashion.
Semi-Conservative
- Each strand is a template
- Remains unaltered
The steps in the semi-conservative fashion?
Unwind
Seperate
Each strand is a ‘template’
IN DNA replication we start with one ___ to these____ to these.
Mother strand -> 2 strands (One strand from mother, one identical)
2->4 Strands (Maternal/new strand, daughter/new strand)
T/F Without mutations there would be no evolution.
TRUE
The initiation of DNA replication starts at…
Specific points of origin, sequences recognized by enzymes.
In Bacteria there is ____ origin of replication.
One
Enzymes in the Initiation Phase?
HTSPD
Helicase Topoisomerase (Single-strand DNA binding proteins) Primase DNA Polymerase III
This enzyme unwinds & seperates the double helix. How?
Helicase - breaks hydrogen bonds
Which enzyme forms the replication fork?
Helicase!
The leading strand opens in the __-__ direction and is ________.
3-5, continuous
Lagging stand opens in the __-__ direction and is ____________.
5-3, discontinuous
This enzyme alleviates strain and periodically repairs cuts in strand (relieving pressure & tension)
Topoisomerase
This guy prevents re-annealing, but isn’t an ______.
Single-Strand DNA Binding Proteins
Isn’t an enzyme
This binds single stranded DNA & acts as the RNA primer.
Primase
Primase is responsible for making a ______ ________ _______ as ____-___.
Hybrid Double Helix as dsDNA-RNA
After primase works, the ds-NA is ready to be bound by
Polymerase
This enzyme begins the synthesis of new DNA.
Polymerase
The new DNA strand is synthesized in the __-__ direction.
5-3
This is called the leading strand because…
It can continuously synthesize
DNA Polymerase III kicks off the __ _____ _______ and only adds to the __’ end.
2 extra phosphates, and adds to the 3’ end.
Nucloside triphoshphates, are added to the
3 Prime end only (ATP, GTP, CTP, TTP)
The energy for the reaction to occur comes from:
Nucleotides
Once DNAP3 is involved, DNA _______ and is ______.
Elongates, Read
The lagging strand, on the other side, opens in the __-__ direction
3-5
These are short newly synthesized DNA fragments on the lagging strand.
Okazaki Fragments
On the lagging strand this makes RNA primer.
Primase
When primer is completed, _____ synthesizes addding a NTP to the __’ end.
DNAP3
3’
As it moves towards the right it will…
Hit another RNA primer & stop
When it hits another RNA primer, the DNAP3
Bumps Off
DNA->______->______->_____->
RNA PRIMER->DNA->RNA PRIMER
The next enzyme that comes along is ______ and it moves from __-__’
DNAP1
moves 5-3
What does DNAP1 do?
Removes ribonclueotide from RNA primer & replaces with deoxynucleotide.
Can DNAP1 join the final nucleotide?
No
So who comes in to seal the deal?
DNA Ligase
T/F There are terminal RNA primers @ very ends of DNA molecules.
TRUE
How do we get rid of the RNA primers?
Removal & replacement where a 3’ end available or No replacement and lagging strand is shorter.
After 2 generations of replication?
Leading strand replicates shorter
Lagging strand now longer
At the end of each DNA sequence is ‘junk DNA’ containing 100’s to 1000’s of repeats called:
Telomeres
Telomeres act as a _________ doing this to the organisms genes.
Buffer - Protecting
An enzyme called __________ catalyzes the lengthening of telomeres.
Telomerase - active in gametes & stem cells, turns off when mature.
