Week 4 Flashcards
(46 cards)
Replication
biological process of producing two identical replicas of DNA from one original DNA molecule
semiconservative replication
after one round of replication, every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA. Then, during the second round of replication, the hybrids would separate, and each strand would pair with a newly synthesized strand.
dispersive replication
every round of replication would result in hybrids, or DNA double helices that are part original DNA and part new DNA. Each subsequent round of replication would then produce double helices with greater amounts of new DNA.
conservative replication
after one round of replication, half of the new DNA double helices would be composed of completely old, or original, DNA, and the other half would be completely new. Then, during the second round of replication, each double helix would be copied in its entirety
equilibrium density centrifugation
method for the separation of cells, cell organelles, macromolecules, or other particles of different densities by centrifugation in a solution that increases in solute concentration, and hence in density
templates
the strand used by DNA polymerase or RNA polymerase to attach complementary bases during DNA replication or RNA transcription
bidirectional replication
replicating DNA in two directions at the same time resulting in a leading strand (were replication occurs more rapidly) and a lagging strand (with slower replication)
origin of replication
a particular sequence in a genome at which replication is initiated
DNA helicase
main function is to unpack an organism’s genes. They are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands
single stranded binding protein
binds to single-stranded regions of DNA. it
prevents the strands from hardening too early during replication,
it protects the single-stranded DNA from being broken down by nucleases during repair, and
it removes the secondary structure of the strands so that other enzymes are able to access them and act effectively upon the strands
DNAA
protein that activates initiation of DNA replication in bacteria
DNAB
DnaB helicase is an enzyme in bacteria which opens the replication fork during DNA replication
DNAC
a loading factor for helicase dnaB
DNAG
synthesizes short strands of RNA known as oligonucleotides during DNA replication
sliding clamp
a protein complex that serves as a processivity-promoting factor in DNA replication. As a critical component of the DNA polymerase III holoenzyme, the clamp protein binds DNA polymerase and prevents this enzyme from dissociating from the template DNA strand
DNA polymerase III
holoenzyme: is the primary enzyme complex involved in prokaryotic DNA replication
primer
short single-stranded nucleic acid utilized by all living organisms in the initiation of DNA synthesis
clamp loading complex
loads clamp onto their associated DNA template strands by specialized proteins known as “sliding clamp loaders”, which also disassemble the clamps after replication has completed
leading stand
a single DNA strand that, during DNA replication, is replicated in the 3’ – 5’ direction (same direction as the replication fork)
lagging strand
strand of nascent DNA whose direction of synthesis is opposite to the direction of the growing replication fork
Okazaki fragment
short sequences of DNA nucleotides (approximately 150 to 200 base pairs long in eukaryotes) which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication
mismatch mutation
mismatched bases include a G/T or A/C pairing. Mismatches are commonly due to tautomerization of bases during DNA replication
exonuclease
enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain
hemimethylated
when only one of two (complementary) strands is methylated
