Ch:15 DNA Replication Flashcards
What is the duty of topoisomerase?
To help relieve strain in the double helix
- As the double helix untwisted, it caused a tighter twisting and some additional strain ahead of replication fork.
Replication of DNA begins at sites called __(2 words)__.
replication origins
Eukaryote have _____ origins of replication. Prokaryotes have a ______ origin.
Eukaryotes = multiple origins of replication
Prokaryotes = single origin of replication
The ____(2 words)____ is Y-shaped regions where parental DNA strands are being unwound.
Replication Fork
What makes DNA replication semi-conservative?
The replicated DNA is 1/2 new and 1/2 old (i.e. 1/2 parental, 1/2 daughter)
When DNA unwinds for DNA replication, what stabilizes the unpaired DNA strands?
“single-stranded” binding proteins
The bottom line is this: as the DNA helix opens, ____, ____ and _____ ensure that it will unravel in a coordinate and stabilized unit.
Helicase, topoisomerase and single-stranded binding proteins
The initial nucleotide chain is actually a small RNA stretch, not DNA. This is what is called an _______ and uses the enzyme primase. This enzyme starts an RNA chain using the parental DNA stand as a template.
RNA primer
The two stands are replicated differently; however both are elongated in the 5’ to 3’ direction. One strand is made in a continuous fashion and is called the ____ strand, while the other strand is made in a discontinuous fashion and is called the _____ strand.
Made in a continuous fashion = Leading strand
Made in a discontinuous fashion = Lagging strand
The lagging strand, which is discontinuous, is made in a series of segments which are called _______.
Okazaki fragments
Which directions do the leading and lagging strands grow?
Leading strand grows in the 5’ to 3’ direction
Lagging strand grows in the 3’ to 5’ direction
Okazaki fragments are joined into a continuous span under the direction of _______, to complete the lagging strand.
DNA ligase
Where does DNA replication occur?
In the nucleus
Define job or duties of each of the following:
- Helicase
- DNA polymerase
- Primase
- Ligase
Helicase: unzips DNA
DNA polymerase is the builder. He replicates DNA molecules to build a new strand by adding DNA bases to the separated strands
Primase is the initializer that makes the primer that is actually a piece of RNA. DNA polymerase doesn’t know where to get started without something called a primer
Ligase is the gluer that helps glue DNA fragments together
What is the duty of a telomere?
The “protector”
The telomere is like a body guard that protects important genes from being deleted as cells divide and as DNA strands shorten during replication
