| A | B |
|---|
| Leading strand, lagging strand, Okazaki fragments | The two new strands at replication fork. Lagging strand made as Okazaki fragments due to directionality of polymerase. |
| Exonucleolytic proofreading | Corrects replication. Removes 3' terminal unpaired nucleotide by 3' to 5' exonucleolytic capability of polymerase. |
| Strand-directed mismatch repair | Corrects replication. Replaces strand segment with base mismatch. No methylation in bacteria and nicks in euc. used. |
| DNA primase, DNA ligase, DNA helicase, single-strand DNA-binding (SSB) proteins | Essential components of the replication fork. DNA helicase and primase constitute primosome i bacteria. |
| DNA topoisomerase I and II | Relieves tension in DNA resp. untangles DNA by forming transient single strand resp. double strand break in DNA. |
| Replication origin | Origin of replication bubble and two replication forks. One in bacterial chromosomes, many in eucaryotic. |
| Depurination, deamination | Spontaneous changes in DNA. Depurination removes purine base leaving only backbone, deamination makes uracil from cytosine. |
| Pyrimidine dimer | Dimer of two pyrimidines that forms when exposed to UV radiation, e.g., sunlight. |
| Base excision repair | Repairs various DNA errors. Excises one faulty base using DNA glycosylases and AP endonucleases and inserts new correct. |
| Nucleotide exicision repair | Repairs various DNA errors. Excises strand segment with faulty base(s) and inserts new correct segment. |
| Aminoacyl-tRNA | tRNA with appropriate amino acid coupled. Synthesized by aminoacyl-tRNA synthetase. |
| Ribosome | Ribozyme. Has large and small subunit, tRNAs move through A, P and E sites. Performs peptidyl transferase. |
| Ef-Tu / Ef-1, Ef-G / Ef-2 | Elongation factors in bacteria resp. euc. Speed up translation and (former) improve codon-anticodon base pairing. |
| AUG, Shine-Dalgarno sequence | Start codon. Euc. usually translate from first AUG, bacteria from AUG just downstream of Shine-Dalgarno sequence. |
| UAA, UAG, UGA | Stop codons. Terminate translation by binding release factor that frees polypeptide chain. |
| Proteasome, ubiquitin | The proteasome binds, unfolds and digests (cleaves into short peptides) proteins marked with ubiquitin by ubiquitin ligases. |
