Topic 5 Flashcards
DNA replication is…
semiconservative
DNA polymerase
a group of multisubunit enzymes that catalyze synthesis of DNA
most of our understanding of DNA replication comes from…
studies in prokaryotic cells
properties of all DNA polymerases
- synthesize DNA only in 5’ to 3’ direction (read in 3’ to 5’)
- can add a new deoxyribonucleotide only to 3’ -OH
replication fork
region of DNA synthesis where parental strands separate and two new daughter strands elongate; location of active DNA replication containing the replication macromolecular complex
leading strand
synthesized in a continuous manner
lagging strand
synthesized in a discontinuous manner in direction opposite of movement of replication fork
Okazaki fragments
small pieces of newly synthesized DNA that are joined to form a new DNA strand in lagging strand
primase
enzyme that synthesize Okazaki fragments (no 3’ OH required)
exonuclease
enzyme activity that hydrolyzes (degrades) DNA or RNA from their ends
RNAse H
exonuclease that degrades the RNA strand of RNA-DNA hybrids
DNA ligase
enzyme that seals breaks in DNA strand
There are _________ DNA polymerases with ___________.
different, similar functions
clamp loading proteins
loads clamp proteins onto replication fork at primer
sliding clamp proteins
load and hold polymerase onto template
helicases
enzymes that catalyze the unwinding of parental DNA in ATP dependent manner
single-stranded DNA-binding proteins
stabilize the unwound single-stranded template DNA
topoisomerase
enzymes that catalyze the reversible breakage and rejoining of DNA strands to relieve torsion caused by unwinding of DNA
The enzymes involved in DNA replication coordinate and synthesize both strands…..
simultaneously
origins of replication (original)
serves as binding sites for the protein complex that initiates the replication process
autonomously replicating sequence (ARS)
an origin of DNA replication in yeast
origin recognition complex (ORC)
6 subunit complex that recruits other proteins (like helices) and recognizes core sequence and bind to it to initiate formation of replication bubble
ori of eukaryotic chromosomes first studied in..
yeast
telomerase
consists of (G-rich) repeats of simple-sequence DNA that is complementary to telomeric DNA (overhanging); also allows prokaryotic DNA to replicate as a linear molecule in yeast
reverse transcriptase
a DNA polymerase that uses an RNA template
Why is reverse transcriptase activity of telomerase necessary?
DNA polymerase cannot replicate the extreme 5’ end
As we age, telomeres….
become shorter
The _______ of DNA replication is critical to cell reproduction. Usually….
accuracy, one in 10^9
what is the rate of error frequency for simple hydrogen bonding of complementary base pairs during replication
1/100 to 1/1000 incorrect
Active selection of correct base by polymerase based on conformation of the expected base accuracy
1/10^5 to 1/10^6 incorrect
proofreading by polymerase accuracy
1/10^7 to 10^8 incorrect
DNA repair mechanisms
increase fidelity and repair from damage like UV light and carcinogens
proofreading
selective removal of mismatched bases by DNA polymerase
primary function or telomeres
to protect chromosome ends from degradation
telomerase activity can be detected from…
both lagging and leading strand
