DNA Structure and Replication Flashcards
origin of replication
the point in the DNA at which replication begins; characterized by a particular sequence of nucleotides (the ORI sequence) containing a large number of A-T bonds
ssDNA
single-stranded DNA; in DNA replication, the DNA after it is separated to serve as the template for replication
dsDNA
double-stranded DNA; two DNA strands with complementary base-pair sequences joined by hydrogen bonds
replication fork
point at which the two DNA strands begin to separate for replication
replication bubble
gap in the DNA formed as the replication fork expands
helicase
enzyme that binds to the ORI sequence and unwinds the dsDNA at replication forks
single-strand binding proteins
proteins that bind to and stabilize the ssDNA after helicase unwinds it
primase
enzyme that builds an RNA primer to begin DNA replication; one primer is used for the leading strand, and several primers are used on the lagging strand to create Okazaki fragments
topoisomerase
enzyme that prevents the double helix from becoming “overwound” during DNA replication by breaking one strand, turning it, and then rejoining the strand together
DNA polymerases
enzymes that synthesize new DNA strands in the 5’ to 3’ direction using the parental DNA is a template; in DNA replication, DNA polymerase III adds nucleotides to the 3’ end of the RNA primer, and DNA polymerase I removes the RNA primer and replaces it with DNA
ligase
joins together fragments of DNA; in DNA replication, joins the newly replaced primer DNA to the leading strand and joins the Okazaki fragments together on the lagging strand
sliding clamp
binds DNA polymerase III to the DNA, preventing the polymerase from detaching
leading strand
newly formed ssDNA complementary to the parental DNA, synthesized continuously towards the replication fork as it expands
lagging strand
complementary ssDNA synthesized with polymerase moving away from the replication fork; synthesized in several small segments called Okazaki fragments
Okazaki fragment
a small segment of DNA formed on the lagging strand using an RNA primer