Chapter 12

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36 Cards. Created by Alizabeth ().
DNA Replication and Recombination

Semiconservative Replication

Replication in which the two nucleotide strands of DNA separate, each serving as a template for the synthesis of a new strand. All DNA replication is semiconservative.

Equilibrium Density Gradient Centrifugation

Method used to separate molecules or organelles of different density by centrifugation.


Unit of replication, consisting of DNA from the origin of replication to the point at which replication on either side of the origin ends.

Replication origin

Sequence of nucleotides where replication is initiated.

Theta replication

Replication of circular DNA that is initiated by the unwinding of the two nucleotide strands, producing a replication bubble. Unwinding continues at one or both ends of the bubble, making it progressively larger. DNA replication on both of the template strands is simultaneous with unwinding until the two replication forks meet.

Replication Bubble

Segment of a DNA molecule that is unwinding and undergoing replication.

Replication Fork

Point at which a double-stranded DNA molecule separates into two single strands that serve as templates for replication.

bidirectional replication

Replication at both ends of a replication bubble.

Rolling-circle replication

Replication of circular DNA that is initiated by a break in one of the nucleotide strands, producing a double-stranded circular DNA molecule and a single-stranded linear DNA molecule, the latter of which may circularize and serve as a template for the synthesis of a complementary strand.

DNA Polymerase

Enzyme that synthesizes DNA.

Continuous replication

Replication of the leading strand in the same direction as that of unwinding, allowing new nucleotides to be added continuously to the 3' end of the new strand as the template is exposed.

Leading strand

DNA strand that is replicated continuously.

Discontinuous replication

Replication of the lagging strand in the direction opposite that of unwinding, which means that DNA must be synthesized in short stretches (Okazaki fragments)

Initiator Protein

Binds to an origin of replication and unwinds a short stretch of DNA, allowing helicase and other single-strand-binding proteins to bind and initiate replication.

DNA helicase

Enzyme that unwinds double-stranded DNA by breaking hydrogen bonds.

Okazaki Fragment

Short stretch of newly synthesized DNA. Produced by discontinuous replication on the lagging strand, these fragments are eventually joined together.

Single-strand-binding (SSB) protein

Binds to single-stranded DNA in replication and prevents it from annealing with a complementary strand and forming secondary structures.

DNA gyrase

E. Coli topoisomerase enzyme that relieves the torsional strain that builds up ahead of the replication fork.


Enzyme that synthesizes a short stretch of RNA on the DNA template; functions in replication to provide a 3'-OH group for the attachment of a DNA nucleotide.


Short stretch of RNA on a DNA template; provides a 3'-OH group for the attachment of a DNA nucleotide at the initiation of replication.