Lecture 3: Replication and Transcription Flashcards
(35 cards)
DNA replication is ________. Each strand in the double
helix acts as a template for synthesis of a new, complementary
strand
semiconservative
New DNA is made by enzymes called ________, which
require a single stranded template, a primer with 3’OH and dNTPs
DNA polymerases
During DNA replication, one new strand (the leading strand) is
made as a continuous piece. The other (__________) is
made in small pieces→Okazaki Fragments
the lagging strand
DNA replication requires other enzymes in addition to DNA
polymerase, including ______, _______-, _______, and _______
DNA primase, DNA helicase, DNA ligase,
and topoisomerase
where does the replication fork form?
where the DNA strands are seperated
Leading strand synthesis, where DNA polymerase moves (nearly)
continuously ________ in the same direction as the replication fork
5’ to 3’
what creates okakazi fragments?
RNA primers being added “backwards”
what is another name for topoisomerase?
DNA gyrase
________:
* always need a template
* can only add nucleotides to the 3’ end of a DNA strand
* require a pre-existing chain or short stretch of nucleotides
called an RNA primer
* proofread, or check their work, removing the vast majority of
“wrong” nucleotides that are accidentally added to the chain
DNA polymerases
DNA polymerases can sometimes degrade pre-existing DNA accidentally… how do we fix this?
exonuclease activity
which end of DNA does DNA polymerase add nucleotides to?
3’ hydroxyl group
If wrong dNTP is accidentally
incorporated, the polymerase is
inhibited from further extension… how do we fix this?
proofreading! removes the mismatch and extension continues by using exonuclease activity (3’-5’)
there are ______ DNA polymerases in E Coli
five
DNA polymerase _____ and _____ are involved in DNA repair
I and II
DNA poly _____ is the enzyme responsible for replication
III
when is DNA poly II activated?
when damage is present, not normally found in cell
which of the E Coli DNA polymerases have exonuclease (3’-5’) activity?
all of them, DNA I-III
which of the E Coli DNA polymerases have exonuclease (5’-3’) activity?
DNA poly I
T/F: DNA poly IV and V do not have proof-reading
true!!!! they are only used as desperation tactics
_________: the number of nucleotides that a polymerase can
incorporate into DNA during a single template-binding event,
before dissociating from a DNA template.
* The overall efficiency of DNA synthesis increases when the
processivity of a polymerase increases
Processivity
higher processivity means….
a better enzyme!!
______: refers to its ability to accurately replicate a template
Fidelity
which DNA poly has the best processivity?
DNA poly III
which DNA poly have high fidelity? low fidelity?
high: I-III
low: IV and V
