DNA replication
a molecule of DNA is copied
transformation
a change in genotype and phenotype due to the assimilation of external DNA by a cell
double helix
two strands and spacing of nitrogenous bases along them
antiparallel
two sugar-phosphate backbones, their subunits run in opposite directions
semiconservative model
Watson and Crick's model predicts that when a double helix replicates, each of the two daughter molecules will have one old strand, from the parental molecule, and one newly made strand.
origins of replication
short stretches of DNA having a specific sequence of nucleotides
replication fork
a Y-shaped region where the parental strands of DNA are being unwound
helicases
enzymes that untwist the double helix at the replication forks, separating the two parental strands and making them available as template strands
single-strand binding proteins
bind to the unpaired DNA strands, keeping them from re-pairing. The untwisting of the double helix causes tighter twisting and strain ahead of the replication fork.
topoisomerase
helps relieve this strain by breaking, swiveling, and rejoining DNA strands.