33 terms

Chapter 14 DNA Replication

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In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine ... cytosine
After DNA replication is completed, _____.
each new DNA double helix consists of one old DNA strand and one new DNA strand
The first step in the replication of DNA is catalyzed by _____.
helicase
The action of helicase creates _____.
replication forks and replication bubbles
Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?
DNA polymerase can assemble DNA only in the 5' to 3' direction
The synthesis of a new strand begins with the synthesis of a(n) _____.
RNA primer complementary to a preexisting DNA strand
An old DNA strand is used as a _____ for the assembly of a new DNA strand.
template
Short segments of newly synthesized DNA are joined into a continuous strand by _____.
ligase
After replication is complete, the new DNAs, called _________, are identical to each other.
daughter DNA
The enzyme that can replicate DNA is called
DNA Polymerase
During DNA replication, an open section of DNA, in which a DNA Polymerase can replicate DNA, is called a
replication fork
The new DNA strand that grows continuously in the 5 to 3 direction is called the
leading strand
____________ are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.
Okazaki Fragments
What catalyzes DNA synthesis?
DNA Polymerase
What are primers?
short sequences that allow the initiation of DNA synthesis
Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?
phosphate groups
Which of the following enzymes creates a primer for DNA polymerase
Primase
Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?
Topoisomerase
One cycle of replication will produce ___daughter DNA molecules, each with one parental strand and one newly synthesized strand.
two
A second cycle of replication produces ____ daughter DNA molecules.
four
Topoisomerase
cuts, swivels, and rejoins DNA strands ahead of the replication fork
Helicase
breaks the hydrogen bonds between parental DNA strands and unwinds the double helix
Single-strand binding proteins
bind to the single strands of DNA, preventing them from re-forming hydrogen bonds with each other and allowing synthesis to occur in both strands.
DNA Polymerase III
synthesizes the new strands, but requires an existing 3 hydroxyl to add nucleotides
Primase
creates short RNA primers, initiating DNA synthesis on both template strands
DNA Polymerase I
removes the RNA primers and replaces them with DNA nucleotides
On the lagging strand, DNA ligase
joins Okazaki fragments by forming phosphodiester bonds between them, thus completing DNA replication.
leading strand
daughter strand elongates toward replication fork, only one primer needed, and made continuously
lagging strand
made in segments, daughter strand elongates away from replication fork, multiple primers needed
both strands
synthesized 5 to 3
Step one of lagging strand synthesis
A new fragment begins with DNA polymerase III binding to the 3' end of the most recently produced RNA primer, primer B in this case, which is closest to the replication fork. DNA pol III then adds DNA nucleotides in the 5' to 3' direction until it encounters the previous RNA primer, primer A.
Step two of lagging strand synthesis
DNA pol III falls off and is replaced by DNA pol I. Starting at the 5' end of primer A, DNA pol I removes each RNA nucleotide and replaces it with the corresponding DNA nucleotide. (DNA pol I adds the nucleotides to the 3' end of fragment B.) When it encounters the 5' end of fragment A, DNA pol I falls off, leaving a gap in the sugar-phosphate backbone between fragments A and B.
Step three of lagging strand synthesis
DNA ligase closes the gap between fragments A and B.