DNA Polymerases exam Flashcards
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DNA Polymerase
An enzyme that synthesizes new DNA strands during replication.
In which direction do DNA polymerases synthesize new DNA strands?
From the 5' to 3' direction.
DNA Polymerase III
The primary enzyme responsible for DNA strand elongation in prokaryotes.
What are the two critical requirements for DNA polymerases to function?
A template strand and a primer.
Template Strand
The old or parental DNA strand that serves as a guide for building new DNA strands.
Primer
A short RNA molecule that provides a free 3' hydroxyl group necessary for DNA strand extension.
What enzyme synthesizes the RNA primer?
Primase.
What happens to the RNA primer after it has served its purpose?
It is replaced by DNA polymerase I.
Primase
The enzyme that synthesizes the RNA primer.
DNA Polymerase I
The enzyme that replaces the RNA primer with DNA.
What is the role of the free 3' hydroxyl group in DNA replication?
It is required for the elongation of the new DNA strand.
How do DNA polymerases know which nucleotides to add during replication?
They base pair the free nucleotides with the template strand.
What is the significance of the 5' and 3' ends in DNA structure?
The 5' end has a free phosphate group, and the 3' end has a free hydroxyl group.
What is the function of DNA polymerases in general?
To build new DNA strands by adding nucleotides to a pre-existing strand.
Why can't DNA polymerases start synthesizing a new strand from scratch?
They require a primer to provide a free 3' hydroxyl group.
What is the role of DNA polymerase III in prokaryotic cells?
It is the primary enzyme for elongating new DNA strands.
What does the term 'anti-parallel' mean in the context of DNA structure?
The two strands of DNA run in opposite directions (5' to 3' and 3' to 5').
What is the role of the enzyme primase?
To synthesize the RNA primer needed for DNA polymerase to start replication.
Why is the RNA primer necessary for DNA replication?
It provides the free 3' hydroxyl group required for DNA polymerase to extend the DNA strand.
What happens to the RNA primer during DNA replication?
It is eventually removed and replaced by DNA polymerase I with DNA.
What is the directionality of new DNA strand synthesis?
Always from 5' to 3'.
What is the function of DNA polymerase I?
To remove and replace the RNA primer with DNA nucleotides.
What is the role of the template strand in DNA replication?
It serves as a guide for the new DNA strand being synthesized.
What is the primary enzyme for DNA strand elongation in prokaryotes?
DNA Polymerase III.
What is required for DNA polymerase to elongate a new DNA strand?
A free 3' hydroxyl group provided by a primer.
What is the role of DNA polymerase in DNA replication?
To synthesize new DNA strands by adding nucleotides to an existing strand.
What is the function of the enzyme primase?
To synthesize the RNA primer needed for DNA polymerase to start replication.