chapter 14 Flashcards
What experimental evidence proved DNA is the hereditary material?
- Hershey and Chase
- DNA contains P and not S
- proteins contain S and not P
What is the semiconservative replication hypothesis?
the parental strands separate and each become a template for the synthesis of the daughter strand
What is the conservative replication hypothesis?
the parental strands temporarily turn out from the helix to become a template; an entire new helix will be made
What is the dispersive replication hypothesis?
the parental helix is cut at intervals to synthesize DNA is short segments
What is DNA polymerase?
- carries out replication
DNA polymerase functions ONLY in the ____________ direction.
5’ –> 3’
What must DNA polymerase have to function?
a second strand to serve as a template
What are the different types of DNA polymerase?
-prokaryotes/bacteria (5): DNA polymerase I-V
-eukaryotes (14): DNA polymerase a (alpha) - v (nu), o (sigma)
Where does the energy for synthesis come from?
dNTP, dATP, dGTP, dTTP, dCTP
What are the molecules involved in opening the helix?
- helicase
- SSBPs
- topoisomerase
What is the function of helicase?
catalyzes the separation of the DNA strands to open the the helix
What is the function of SSBPs?
stabilize the single strand of DNA
What is the function of topoisomerase?
breaks down/rejoins DNA double helix to relieve twisting forces that are caused by the opening of the helix
What are the molecules involved in leading-strand synthesis?
- primase
- DNA polymerase III
- sliding clamp
What is the function of primase in leading strand synthesis?
catalyzes the synthesis of RNA primer
What is the function of DNA polymerase III in leading strand synthesis?
extends the leading strand
What is the function of the sliding clamp in leading strand synthesis?
holds the polymerase in place during strand extension
What are the molecules involved in lagging-strand synthesis?
- primase
- DNA polymerase III
- sliding clamp
- DNA polymerase I
- ligase
What is the function of primase during lagging-strand synthesis?
catalyzes the synthesis of RNA primer on the Okazaki fragment
What is the function of DNA polymerase III in lagging-strand synthesis?
extends the Okazaki fragment
What is the function of the sliding clamp in lagging-strand synthesis?
holds DNA polymerase in place during strand extension
What is the function of DNA polymerase I in lagging-strand synthesis?
removes the RNA primer and replaces it with DNA
What is the function of ligase in lagging-strand synthesis?
catalyzes the joining of the Okazaki fragments into 1 continuous strand
Describe the steps of lagging-strand synthesis.
- primer is added
- the first fragment is synthesized
- second fragment is synthesized
- primer is replaced, leaving slight gap
- gap is closed
