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.
mismatch pair
A repair system that removes mismatched bases from newly synthesized DNA strands.
nucleotide-excision repair
A mechanism of DNA repair in which oligonucleotides containing damaged bases are removed from a DNA molecule.
Okazaki fragment
A short DNA fragment synthesized to form the lagging strand of DNA.
origin of replication
A specific DNA sequence that serves as a binding site for proteins that initiate replication.
origin recognition complex (ORC)
A protein complex that initiates DNA replication at eukaryotic origins.
photo-reactivation
A mechanism of DNA repair in which solar energy is used to split pyrimidine dimers.
primase
An RNA polymerase used to initiate DNA synthesis.
processed pseudogene
A pseudogene that has arisen by reverse transcription of mRNA.
proofreading
The selective removal of mismatched bases by DNA polymerase.
pyrimidine dimer
A common form of DNA damage caused by UV light in which adjacent pyrimidines are joined to form a dimer.
Rad51
The eukaryotic homolog of RecA.
RecA
A protein that promotes the exchange of strands between homologous DNA molecules during recombination.
recombinational repair
The repair of damaged DNA by recombination with an undamaged homologous DNA molecule.
replication fork
The region of DNA synthesis where the parental strands separate and two new daughter strands elongate.
retrotransposons
A transposable element that moves via reverse transcription of an RNA intermediate.
retrovirus
A virus that replicates by making a DNA copy of its RNA genome by reverse transcription.
reverse transcriptase
A DNA polymerase that uses and RNA template.
RNase H
An enzyme that degrades the RNA strand of RNA-DNA hybrid molecules.
SINE (short interspersed element)
A family of highly repeated retrotransposons in mammalian genomes.
single stranded DNA-binding protein
A protein that stabilizes unwound DNA by binding to single stranded regions.
site-specific recombination
Recombination mediated by proteins that recognizes specific DNA sequences.
somatic hypermutation
The introduction of multiple mutations within rearranged immunoglobulin variable regions to increase antibody diversity.
T cell receptor
A t lymphocyte surface protein that recognizes antigens expressed on the surface of other cells.
telomerase
A reverse transcriptase that synthesizes telomeric repeat sequences at the ends of chromosomes from its own RNA template.
telomere
A repeat of simple sequence DNA that maintains the ends of linear chromosomes.
topoisomerase
An enzyme that catalyzes the reversible breakage and rejoining of DNA strands.
transcription-coupled repair
The preferential repair of damage to transcribed strands of DNA.
translesion DNA synthesis
A form of repair in which specialized DNA polymerases replicate across a site of DNA damage.
transposable element
transposon
transposon
A DNA sequence that can move to different positions in the genome.
