Chapter 14

endonuclease

enzymes that cleave the phosphodiester bond within a polynucleotide chain

exonuclease

enzymes that cleave nucleotides one at a time from the end of a polynucleotide chain 

helicase

During replication, the strand that is replicated in short fragments and away from the replication fork

leading strand

strand that is synthesized continuously in the 5’-3’ direction, which is synthesized in the direction of the replication fork

Ligase

Enzyme that catalyzes the formation of a phosphodiester linkage between the 3’ OH and 5’ phosphate ends of the DNA 

mutation

variation in the nucleotide sequence of a genome

Okazaki fragment

DNA fragment that is synthesized in short stretches on the lagging strand

primase

enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA pol to start synthesis of a new DNA strand

primer 

Short stretch of nucleotides that required to initiate replication; in the case of replication, the primer has RNA nucleotides

replication fork

y-shaped structure formed during initiation of replication

single- strand binding protein

during replication, protein that binds to the single-stranded DNA; this helps in keeping the two strands of DNA apart so that they may serve as templates 

sliding clamp

ring shaped protein that holds the DNA pol on the DNA strand

telomerase 

enzyme that contains a catalytic part and an inbuilt RNA template; it functions to maintain telomeres at chromosome ends 

Telomere

DNA at the end of linear chromosomes

topoisomerase

enzyme that prevents overwinding of DNA when DNA replication os taking place