DNA Replication Flashcards
What type of replication does DNA undergo?
Semi-conservative.
What is each DNA strand composed of during replication?
One existing (parent) half and one newly synthesized (daughter) half.
Who confirmed the semi-conservative replication model and in what year?
Meselson and Stahl, 1957.
What binds to specific sites on the DNA to start replication?
Proteins.
What enzyme unwinds the double helix?
DNA helicase.
What prevents DNA strands from reannealing during replication?
Single-Stranded Binding Proteins (SSBs).
What enzyme relieves tension in the DNA strands?
DNA gyrase and topoisomerase.
What is the role of DNA Polymerase III?
Builds the complementary strand by adding free DNTP
In which direction does DNA Polymerase III synthesize DNA?
5’ to 3’.
What provides the starting point for DNA Polymerase III?
An RNA primer inserted by a primase enzyme.
What type of energy drives the addition of nucleotides?
Energy from the breaking of phosphate bonds.
What is the leading strand?
The strand synthesized continuously in the 5’ to 3’ direction.
What is the lagging strand?
The strand synthesized discontinuously in short Okazaki fragments.
What joins Okazaki fragments together?
DNA ligase.
What removes RNA primers and replaces them with DNA?
DNA Polymerase I.
What happens to the DNA strands after they are built?
They rewind to form a double helix.
What role does DNA Polymerase II have in replication?
Recognizes hydrogen bonding errors and corrects mismatches.
What are telomeres?
Long, repetitive, non-coding DNA sequences at the ends of chromosomes.
What is the function of telomeres?
Act as buffer zones to prevent loss of valuable genetic material.
What are replication origins?
Specific sites on DNA where replication begins.
What bonds are broken to unwind the DNA double helix?
Hydrogen bonds.
What is an Okazaki fragment?
Short DNA fragment on the lagging strand.
How does DNA helicase function?
By breaking hydrogen bonds to separate DNA strands.
Why are RNA primers necessary?
DNA Polymerase III can only add nucleotides to an existing strand.
What is a replication fork?
The Y-shaped region where DNA is split into two strands for replication.
What is the purpose of DNA gyrase?
Prevents supercoiling by cutting and resealing DNA strands.
How does DNA Polymerase III maintain accuracy?
By proofreading and correcting mismatched base pairs.
What happens if DNA Polymerase III detects an error?
It removes the incorrect nucleotide and inserts the correct one.
Why is DNA replication described as semi-discontinuous?
Leading strand is synthesized continuously; lagging strand discontinuously.
What enzyme synthesizes the RNA primers?
Primase.
