Chapter 2 -DNA Replication and Repair

Question	Answer
DNA synthesis direction	5′-3′
Region of DNA that initiates transcription of a particular gene	Promoter
Y-shaped region along DNA template where leading and lagging strands are synthesized	Replication Fork
Unwinds DNA template at replication fork	Helicase
Prevent strands from reannealing	SSB (Single-stranded bindind) proteins
Create break in the helix to add or remove supercoils	DNA topoisomerases
Makes an RNA primer where DNA polymerase III can initiate replication	Primase
Initiate replication	DNA polymerase III
Small fragments found only in the lagging strand	Okazaki
Defective in xeroderma pigmentosum (inability to repair DNA pyrimidine dimers caused by UV exposure)	Nucleotide excision repair
Important in repair of spontaneous/toxic deamination	Base excision repair
Defective in Lynch syndrome	Mismatch repair
Defective in ataxia telangiectasia and Fanconi anemia	Nonhomologous end joining
Defective in breast/ovarian cancers with BRCA1 mutation.	Homologous recombination
Mutation in this area results a dramatic reduction of gene transcription	Promoter
Increase expression of a gene on the same chromosome	Enhancer
Decrease expression of a gene on the same chromosome	Silencer
mRNA start códons	AUG
mRNA stop códons	UGA UAA UAG
Exclusive enzyme of eukaryotic replication	Promoter

Resource summary

	Created by USMLE STEP1 about 6 years ago