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Chapter 13 DNA
DNA Role in Heredity
27
Biology
Undergraduate 1
04/02/2011

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Term
Purtines
Definition
Adenine(A) and Guanine(G)
Term
Pyrimidines
Definition
Cytosine(C), Thymine(T) and Uracil(U)
Term
DNA Polymerase
Definition
Enzyme catalyzed the reaction
Term
Semiconservative Replication
Definition
In which each parent strand serves as a template for a new strand, and the two new DNA molecules each have one old and one new strands
Term
Dispersive Replication
Definition
In which fragments of the original DNA molecule serve as a template for assembling two new molecules, each containing random segments from both
Term
Conservative Replication
Definition
In which the original double helix serves as a template for but does not contribute to s new double helix. Two strands come back together after replication
Term
5' end
Definition
a free(not connected to another nucleotidde) 5' phosphate group
Term
3' end
Definition
is a free 3' hydroxyl group
Term
Complementary base pairing
Definition
the amount if adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. As a result, the total abundance of purines equals the total abundance of pyrimidines. Every base pair consists of one purine and one pyrimidine.
Term
Meselson and Stahl
Definition
DNA is produced by semiconservativereplication proven by using density gradiet centrifugation
Term
DNA Replication
Definition
ocuurs when the two strands open out, new nucleotides line up opposite the old complementary bases, and DNA polymerase catalyzes their addition to the new strand.
Term
Proliferating cell nuclear antigen(PCNA) Sliding Clamp
Definition
does more than just keep the DNA polymerase bound to the DNA, it also helps to oriet the polymerase for binding to the substrate. Additionally binds many other proteins to DNA, these proteins aid in replication and repair
Term
Helicase
Definition
initates replication bu unwinding
Term
Single strand binding proteins(SSB)
Definition
bind to the unwound strands to keep them from reasociating into a double helix
Term
Replication Fork
Definition
The site whereunwinds to expose the bases so that they can act as templates-opens up as a zipper
Term
Leading Strand
Definition
3'-5' direction, so new strand is built continously 5'-3' after primer strand is produced
Term
Lagging Strand
Definition
5'-3' direction so new strand must be built in the 3'-5' direction, but DNA polymerase can only sythesize in 5'-3' direction. So the strand is built discontinously in fragments
Term
DNA Ligase
Definition
Connects together okazaki fragments by closing last gap between fragments
Term
Lagging Strand process
Definition
Each okazaki fragment requires its own primer of the previous fragment. Then DNA polymerase III lays down new DNA by adding nucleotides to one primer until it reaches the primer of the previous fragment. At this point DNA polymerase I removes the old primer and replaces it with DNA
Term
Telomeres
Definition
The ends of eukaryotic chromosomes, they have special sequnces that prevent the ends of chromosomes from attaching to one another
Term
Proofreading
Definition
DNA polymerase mechanism to be able to correct errors in replucation as DNA polymerase makes them
Term
Mismatch Repair
Definition
Mechanism scans DNA immediately after it has been replicate, upon finding a mismatch it recruits other enzymes. These other enzymes cut the DNA strand on both side, removing several nucleotides on either side. DNA polymerase I then fill in the missing
stretch, with DNA ligase closing the last gap
Term
Excision Repair
Definition
Other enzymes search for bases that have been chemicaly modified so they are no longer one of the 4 nucleotides recognized during DNA replication. Upon finding one, they recruit other enzymes to cut the DNA backbone on either side of the damaged base and remove the section of DNA. DNA polymerase I again replaces the missing stretch with DNA ligase closing the last gap
Term
Polymerase III
Definition
The one responsible for DNA replication.
It cannot start strands, builts on the RNA primer chain that Primase creates. Can only add new nucleotides one a strand running from 3'-5', not 5'-3', thuse builds the lagging strand in a discontinous fashion using okazaki fragments.
Term
Polymerase I
Definition
Follows Replication Fork, replacing the Primer strand. Corrects errors when found, replacing missing stretch with DNA that has been removed due to error
Term
DNA backbone
Definition
composed of alternating sugar and phosphates
Term
Structure of Nucleic Acids
Definition
pentose sugar, nitrogenous base, phosphate DNA backbone composed of alternating sugar and phosphate
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