Midterm 2-1 Flashcards
(28 cards)
What are e enzymes for DNA replication
DNA polymerase I and DNA polymerase III, these performed the bulk of DNA replication during cell division, I plays a role in the repair of mutation
How is DnA synthesized
It is synthesized from triphosphates. When a nucleotide triphosphates is attached to the end of a DnA strand, the first phosphate is retained in the DnA structure while the other two phosphates are cut free from the structure
How does DNA polymerase work
It catalyzed DNA from 5’-3’. New nucleotides are added to the 3-carbon hydroxyl on the ribose of an existing strand. The phosphate attached to the 5’ end of the nucleotide triphosphates is attached to the hydroxyl at the 3’ end
How does replication get started
Two strands of DNA are separated to form a bubble of single stranded DNA. As replication from the site of origination, new strands of DNA are synthesized using each single stranded piece of chromosome
What is a replication fork
A structure that moves forward from the sit of origin. It is a y shaped structure that moves along as DNA replication proceeds
How is the helix opened and stabilized
The DNA helicase, and enzyme that opens the double helix to allow enzymes to attach to each strand. Small proteins known as single strand DNA binding proteins bind e single strand DNA and keeps it from re forming double stranded DNA
What does DNA polymerization require
A primer on which to add nucleotides to. The primate enzyme makes short RNA primers to start DNA synthesis
What does topoisomerase do
It’s an enzyme that releases supercooling that can occur when the helix is opened up
What is the leading strand
The DNA synthesis process that pushes toward the replication fork
What is the lagging strand
This is the strand that is synthesized a direction away from the overall movement of the replication fork
What did Okazaki discover
The mechanism of lagging strand synthesis. The short fragments in the theory at the site is called the Okazaki fragments. The lagging ends are eventually put together by polymerase I and DNA ligase
What is replisome
All the enzymes in DNA replication combined, a large macro molecular machine
Explain the need for RNA in the process of DNA replication
DNA polymerases are unable to synthesize DNA from a template strand unless there is an available primer on which to add new nucleotides. RNA polymerase are able to synthesize short RNA primers de novo, and they are utilized during DNA replication to prime new DNA synthesis.
What does helicase do
Catalyzed the breaking of hydrogen bonds between base pairs to open the double helix
What does the single strand DNA binding protein do
Stabilize single strand DNA
What does topoisomerase do
Breaks and rejoins the DNA helix to relieve twisting forces cause. Y the opening of the helix
What does primase do
Catalyze the synthesis of the RNA primer
What does DNA polymerase III do
Extends the leading strand
What does the sliding clam do
Holds DNA polymerase in place during strand extension
What does primase in the lagging strand do
Catalyze the synthesis of the RNA primer on an Okazaki fragment
What does DNA polymerase III in the lagging strand do
Extends an Okazaki fragment
What does the sliding clamp in the lagging strand do
Holds DNA polymerase in place during strand extension
What does DNA polymerase I do
Removes DNA polymerase in place during strand extension
What does DNA ligase do
Catalyzed the joining of Okazaki fragments into continuous strands
