WCU Bio 431 - Exam 1 Questions
and Answers
Helicase - ANSWER-binds at replication fork on single-stranded DNA
pulls DNA through itself, separating the strands and breaking hydrogen bonds using
ATP like a motor
bidirectional
DNA gyrase - ANSWER-form of topoisomerase I for bacteria only
relieves supercoils by cutting, rotating and rejoining single strands
Topoisomerase I - ANSWER-cleaves single strand of DNA
only fixes one twist at a time
does not require energy
works before replication fork
Topoisomerase II - ANSWER-cleaves double strand DNA
requires energy
Primase - ANSWER-specialized RNA polymerase
makes short RNA sequences (primers)
recruited at replication fork
doesn't require promoter or primer
activity greatly increased when associated with helicase and ssDNA
Single stranded binding proteins - ANSWER-binds to ssDNA before polymerase and
keeps it straight
DNA sliding clamp - ANSWER-increases processivity
keeps DNA pol associated with template strand
DNA pol still disengages from DNA but clamp holds it and binds it to primer:template
junction
highly conserved
PCNA - ANSWER-proliferating cell nuclear antigen
human sliding clamp
essential processivity factor for DNA replication and repair
RNase - ANSWER-enzyme that removes RNA primers that are bound to DNA (RNA-
DNA hybrid)
after RNA is degraded a new primer:template junction is formed and DNA pol can
attach and synthesize new DNA
and Answers
Helicase - ANSWER-binds at replication fork on single-stranded DNA
pulls DNA through itself, separating the strands and breaking hydrogen bonds using
ATP like a motor
bidirectional
DNA gyrase - ANSWER-form of topoisomerase I for bacteria only
relieves supercoils by cutting, rotating and rejoining single strands
Topoisomerase I - ANSWER-cleaves single strand of DNA
only fixes one twist at a time
does not require energy
works before replication fork
Topoisomerase II - ANSWER-cleaves double strand DNA
requires energy
Primase - ANSWER-specialized RNA polymerase
makes short RNA sequences (primers)
recruited at replication fork
doesn't require promoter or primer
activity greatly increased when associated with helicase and ssDNA
Single stranded binding proteins - ANSWER-binds to ssDNA before polymerase and
keeps it straight
DNA sliding clamp - ANSWER-increases processivity
keeps DNA pol associated with template strand
DNA pol still disengages from DNA but clamp holds it and binds it to primer:template
junction
highly conserved
PCNA - ANSWER-proliferating cell nuclear antigen
human sliding clamp
essential processivity factor for DNA replication and repair
RNase - ANSWER-enzyme that removes RNA primers that are bound to DNA (RNA-
DNA hybrid)
after RNA is degraded a new primer:template junction is formed and DNA pol can
attach and synthesize new DNA
