Chapter 8 Flashcards
(21 cards)
What is dna replication?
Is semiconservatiev
What stage in eukaryotes does dna replication take place in?
The S phase
What is the organization of the genome in prokaryotes ?
One circular chromosome
What is organization of the genome eukaryotes
There are several linear chromosomes
Where does replication begin ?
At special sites along the dna called origin of replication
Replication occurs bidirectionally
How many Origins of replication are there in prokaryotes and eukaryotes
Prokaryotes = one origin
Eukaryotes multiple origins
What is the first step in DNA replication ?
Proteins recognize the ori , bind to the dna and start to unwind it forming a replication bubble
What is at the end of each replication bubble
The replication fork
What is helicase ?
A protein that binds at the replication for , unwinding the DNA strands
The helicase moves down the DNA as replication continues
What is the single stranded dna binding proteins ?
These proteins bind to the single stranded dna and keep the strands separated and stabilize the single stranded DNA
What is the topoisomerase (dna gyrase)
Binds to the dna nad helps to relieve the torsional stress by breaking , swivelling and redoing the dna strands
What is primase?
Synthesizes an rna primer at 5 prime end of the leading strand and at the 5 prime end of each Okazaki fragment of the lagging strand
DNA pol iii
Using parental dna as a template , synthesizes new dna strand by adding nucleotides to an rna primer or pre existing dna strand
What is dna pol i
Removes rna nucleotides of primer from 5 ‘ end and replaces them with dna nucleotides
What is dna ligase?
Joins Okazaki fragments of lagging strand
On the leading strand it Joins the 3 prime end of dna that replaces the primer to rest of the leading strand
What direction does dna polymerase synthesize in ?
5’ to the 3’ direction
No KNOWN dna polymerase can synthesize DNA de novo
DNA polymerase requires a free 3 PRIME OH GROUP
How does dna polymerase make/elongate a new strand ?
DNA polymerase catalyses the formation of a phosphodiester bond between the 3’-oh group of the first phosphate of the incoming nucleotide
DNA polymerase uses DNTPS as the substrate
What are three things dna polymerase needs to synthesize a complementary strand of dna ?
Template that will direct the synthesis of a complementary strand of dna
Primer to provide a free 3’-OH group to which nucleotides can be added on to
Deoxynucleotide triphosphate
Why does DNA need a primer ?
Because dna polymerase can’t make a new strand of DNA from the template strand , it needs something to add nucleotides on it
What is a leading strand ?
As chains are elongating one is being replicated in a continuous manner
What is the lagging strand?
Chain being replicated in a discontinuous manner
Segments of DNA that make up the lagging strand are called Okazaki fragment S
