MICR 271 Module 4 Questions with Correct
Answers
What type of chromosomes do bacteria contain?
Circular
What direction do circular chromosomes replicate in?
Bi-directional!
What is the oriC?
The origin, where DNA replication begins. This site is AT-rich and thus is separated easier
than G-C regions.
What happens once the DNA strands are seperated?
The replication forks will proceed in opposite directions. This is driven by the replisome,
before the two forks meet at the termination site.
What is the replisome?
Complex of multiple proteins involved in replication.
How are multiple copies of chromosomes created?
When additional rounds of replication begin at the oriC before the prior rounds reach the
termination site.
What are catenated daughter chromosomes?
Chromosomes that are interlocked. This is the result of circular chromosomes replicating.
What is topoisomerase?
,A group of enzymes responsible for managing DNA tangling, unwinding, and winding. They
especially help in the decatenation of catenated daughter chromosomes.
Name one advantage of having circular chromosomes.
The chromosomes will not have to worry about free end, or loss of DNA material after each
replication round.
What is a helicase?
Appears like a whirling molecular machine, that spins the DNA as fast as a jet engine, and
unwinds the double helix into 2 strands.
How are strands copied?
One strand is copied continously, whereas the other strand is copied backwards. The other
strand will be drawn out repeatedly in loops and copied one section at a time.
Explain the bacterial replication process:
1. The helicase will unwind DNA. The lagging strand will be coated with single stranded
DNA binding proteins (SSB) proteins. The primase will produce a RNA primer.
2. DNA Pol III holoenzyme will be attached to DNA through a B-clamp. The t clamp loader
will load the DNA Pol III into the complex.
3. A core enzyme of Pol III will carry out the replication of the leading strand.
4. Two additional Pol III enzymes will carry out the replication of the lagging strand, and
create Okazaki fragments.
, 5. The core enzymes reach the completed region, and will be released as Okazaki fragments
are bound together. DNA Pol I will remove the RNA primer, fill gaps between DNA, and
DNA ligase will join all strands.
What do single stranded DNA binding proteins do?
It has protective functions!
What is a holoenzyme?
Apoenzyme + cofactor (coenzyme), in active form.
What is a core enzyme?
Subunits of an enzyme that are required for catalytic activity.
Explain the eukaryotic replication process:
1. To activate the helicase and the unwinding of the DNA, the helicase is complexed with
additional proteins. Single stranded DNA will be protected by the replication protein A.
2. Helicase will associate indirectly with primase (Pol ∞) to synthesize RNA primer.
3. Polymerase (Pol Ɛ) will be responsible for the creation of the leading strand. Pol 8 will be
responsible for the creation of the lagging strand. Proliferating cell nuclear antigen (PCNA)
load these polymerases into the DNA, and a replication factor C will carry this to DNA.
4. Okazaki fragments are shorter in eukaryotes. RNA primer will be removed by strand
displacement, filled in by Pol 8, and DNA ligase will repair gaps in strands.
Do replication forks work faster in humans or prokaryotes?
Answers
What type of chromosomes do bacteria contain?
Circular
What direction do circular chromosomes replicate in?
Bi-directional!
What is the oriC?
The origin, where DNA replication begins. This site is AT-rich and thus is separated easier
than G-C regions.
What happens once the DNA strands are seperated?
The replication forks will proceed in opposite directions. This is driven by the replisome,
before the two forks meet at the termination site.
What is the replisome?
Complex of multiple proteins involved in replication.
How are multiple copies of chromosomes created?
When additional rounds of replication begin at the oriC before the prior rounds reach the
termination site.
What are catenated daughter chromosomes?
Chromosomes that are interlocked. This is the result of circular chromosomes replicating.
What is topoisomerase?
,A group of enzymes responsible for managing DNA tangling, unwinding, and winding. They
especially help in the decatenation of catenated daughter chromosomes.
Name one advantage of having circular chromosomes.
The chromosomes will not have to worry about free end, or loss of DNA material after each
replication round.
What is a helicase?
Appears like a whirling molecular machine, that spins the DNA as fast as a jet engine, and
unwinds the double helix into 2 strands.
How are strands copied?
One strand is copied continously, whereas the other strand is copied backwards. The other
strand will be drawn out repeatedly in loops and copied one section at a time.
Explain the bacterial replication process:
1. The helicase will unwind DNA. The lagging strand will be coated with single stranded
DNA binding proteins (SSB) proteins. The primase will produce a RNA primer.
2. DNA Pol III holoenzyme will be attached to DNA through a B-clamp. The t clamp loader
will load the DNA Pol III into the complex.
3. A core enzyme of Pol III will carry out the replication of the leading strand.
4. Two additional Pol III enzymes will carry out the replication of the lagging strand, and
create Okazaki fragments.
, 5. The core enzymes reach the completed region, and will be released as Okazaki fragments
are bound together. DNA Pol I will remove the RNA primer, fill gaps between DNA, and
DNA ligase will join all strands.
What do single stranded DNA binding proteins do?
It has protective functions!
What is a holoenzyme?
Apoenzyme + cofactor (coenzyme), in active form.
What is a core enzyme?
Subunits of an enzyme that are required for catalytic activity.
Explain the eukaryotic replication process:
1. To activate the helicase and the unwinding of the DNA, the helicase is complexed with
additional proteins. Single stranded DNA will be protected by the replication protein A.
2. Helicase will associate indirectly with primase (Pol ∞) to synthesize RNA primer.
3. Polymerase (Pol Ɛ) will be responsible for the creation of the leading strand. Pol 8 will be
responsible for the creation of the lagging strand. Proliferating cell nuclear antigen (PCNA)
load these polymerases into the DNA, and a replication factor C will carry this to DNA.
4. Okazaki fragments are shorter in eukaryotes. RNA primer will be removed by strand
displacement, filled in by Pol 8, and DNA ligase will repair gaps in strands.
Do replication forks work faster in humans or prokaryotes?
