Recombination Repair and Genome Editing

Flashcards on DNA Double Strand Breaks (DSBs) and Repair Mechanisms

DNA Double Strand Breaks (DSBs)

The most detrimental lesion introduced into DNA, caused by ionizing radiation, chemical compounds, free radicals, recombination intermediates, DNA replication, transposition, mating type switch in yeast or V(D)J joining.

Homologous Recombination (HR)

A mechanism to repair Double Strand Breaks (DSBs) using information retrieved from sister chromatids.

Non-Homologous End Joining (NHEJ)

A mechanism to repair Double Strand Breaks (DSBs) by ligation of ends without homology.

Exonuclease processing in HR

The ends of the ds break are processed by exonuclease to leave 3` single strand overhangs

Strand invasion in HR

The SS overhangs invade the homologous duplex, followed by DNA strand exchange and DNA synthesis to replace missing information.

Holliday Junction Resolution

The molecules are resolved by branch migration, Holliday Junction resolution and ligation within Homologous Recombination repair of Double Strand Breaks.

Ku70/Ku80 heterodimer

Binds to DSBs in Non-Homologous End Joining (NHEJ) and allows binding of the NHEJ polymerase, nuclease and ligase complexes.

NHEJ Polymerase and Nuclease activity

Acts on DSBs to resect and add nucleotides, creating microhomology between the two DNA ends for guiding end joining in Non-Homologous End Joining.

Error-prone NHEJ

A process that can insert or delete a number of bases at the repair junction.

Template switching

Exchange between the silent and expressed loci, unidirectional, in Trypanosomes through Homologous Recombination Double Strand Break repair.

Antibody diversity

Generated by Non Homologous End Joining Repair of Double Strand Breaks.

V, D, and J segments

Segments of Antibody Genes that rearrange during maturation of B cells.

NHEJ in Antibody Diversity

Non-homologous end joining further increases antibody diversity, leading to increased mutation at the joining sites.

Zinc Finger Nucleases (ZFNs)

Engineered nucleases where the Fok I nuclease is fused with codon-specific recognition modules; used to create DSBs at targeted sites for genome editing.

TALENs

Engineered nucleases where the Fok I nuclease is fused with nucleotide-specific recognition modules to create DSBs at targeted sites for genome editing.

CRISPR-Cas9

An RNA-guided nuclease that becomes activated after the guide RNA base-pairs with the target sites to create DSBs at targeted sites for genome editing.