6. Replications, Maintenance, and Rearrangements of Genomic DNA Flashcards
activation-induced deaminase (AID)
An enzyme expressed in B lymphocytes that deaminates cytosine in DNA to form uracil in the variable regions of immunoglobulin genes. AID is required for both class switch recombination and somatic hypermutation.
antigen
A molecule against which an antibody is directed.
AP endonuclease
A DNA repair enzyme that cleaves next to apyrimidinic or apurinic sites in DNA.
autonomously replicating sequence (ARS)
An origin of DNA replication in yeast.
base-excision repair
A mechanism of DNA repair in which single damaged bases are removed in a DNA molecule.
class switch recombination
A type of region-specific recombination responsible for the association of rearranged immunoglobulin V(D)J regions with different heavy-chain constant regions.
DNA glycosylase
A DNA repair enzyme that cleaves the bond linking a purine or pyrimidine to the deoxyribose of the backbone of a DNA molecule.
DNA ligase
An enzyme that seals breaks in DNA strands.
DNA polymerase
An enzyme catalyzing the synthesis of DNA.
double-strands break
Damage that results in breaks in both complementary strands of DNA.
excinuclease
The protein complex that excises damaged DNA during nucleotide-excision repair in bacteria.
exonuclease
An enzyme that hydrolyzes DNA molecules in either 5’ to 3’ or 3’ to 5’ direction.
gene amplification
An increase in the number of copies of a gene resulting from the repeated replication of a region of DNA.
helicase
An enzyme that catalyzes the unwinding of DNA.
homologous recombination
Recombination between segments of DNA with homologous nucleotide sequences.
immunoglobulin
antibody
lagging strand
The strand of DNA synthesized opposite the direction of movement of the replication fork by ligation of Okazaki fragments.
leading strand
The strand of DNA synthesized continuously in the direction of movement of the replication fork.
LINE (long interspersed element)
Member of a family of highly repeated retrotransposons in mammalian genomes.
long terminal repeat (LTR)
Sequences found at the ends of retroviral DNA that are direct repeats of several hundred nucleotides resulting from reverse transcriptase activity.