Genetics Module 10; Replication and Recombination
Replication in which the two nucleotide strands of DNA separate, and each serves as a template for the synthesis of a new strand. All DNA replication is by this method
Semi Conservative Replication
Site where DNA replication is initiated
Origin of Replication
Unit of replication consisting of DNA from the origin of replication to the point at which replication on either side of the origin ends
Replicon
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
Theta replication
Segment of a DNA molecule that is unwinding and undergoing replication
Replication bubble
Point at which a double-stranded DNA molecule separates into two single strands that serve as templates for replication
Replication fork
Replication at both ends of a replication bubble
Bidirectional replication
Direction of replication
DNA is synthesized in the 5’ to 3’ direction
Enzyme that synthesizes DNA
DNA polymerase
Replication of the leading strand of DNA 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
Continuous replication
Requirements for rpelication
A single-stranded DNA template, Raw materials (deoxyribonucleoside triphosphates - dNTPs) to be assembled into a new nucleotide strand and enzymes and other proteins that "read' the template and assemble the dNTPs into a DNA molecule
DNA strand that is replicated continuously
Leading strand
Replication of the lagging strand of DNA in the direction opposite that of unwinding, which means that DNA must be synthesized in short stretches (Okazaki fragments)
Discontinuous replication
DNA strand that is replicated discontinuously
Lagging strand
Short length of newly synthesized DNA produced by discontinuous replication on the lagging strand; these fragments are eventually joined together
Okazaki fragments
Protein that binds to an origin of replication and causes a short section of DNA to unwind, allowing helicase and other single-strand-binding proteins to attach to the polynucleotide strand
Initiator protein
Enzyme that unwinds double-stranded DNA by breaking hydrogen bonds that exist between the bases of the two nucleotide strands of a DNA molecule
DNA helicase
Protein that attaches tightly to the exposed single-stranded DNA during replication and prevents the formation of secondary structures that would interfere with replication
Single stranded binding proteins
Topoisomerase enzyme that relieves the torsional strain that builds up ahead of the replication fork
DNA gyrase
Enzyme that synthesizes a short stretch of RNA on a DNA template; functions in replication to provide a 3’-OH group for the attachment of a DNA nucleotide
Primase
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
Primer
Enzyme that catalyzes the formation of a phosphodiester bond between adjacent 3’-OH and 5’-phosphate groups in a DNA molecule without adding another nucleotide to the strand
DNA ligase
Process by which DNA polymerases remove and replace incorrectly paired nucleotides in the course of replication
Proof reading
Process that corrects mismatched nucleotides in DNA after replication has been completed. Enzymes excise incorrectly paired nucleotides from the newly synthesized strand and use the original nucleotide strand as a template for replacing them
Mismatch repair
Protein that ensures that replication takes place only once at each origin of replication; required at the origin before replication can be initiated and removed after the DNA has been replicated
Replication liscensing protein
The ends of linear DNA cannot be replicated completely during lagging strand DNA synthesis which leads to a progressive shortening of chromosomes
End-replication problem
A guanine-rich sequence of nucleotides that protrudes beyond the complementary C-rich strand at the end of a chromosome
G-overhang
Ribonucleoprotein enzyme that replicates the ends (telomeres) of eukaryotic chromosomes. The RNA part of the enzyme has a template that is complementary to repeated sequences in the telomere and pairs with them, providing a template for the synthesis of additional copies of the repeats
Telomerase
Exchange of genetic information between homologous DNA molecules
Homologous recombination
DNA consisting of two strands, each of which is from a different chromosome
Heteroduplex DNA
Special structure resulting from homologous recombination that is initiated by single-strand breaks in a DNA molecule
Holliday Junction
Discontinuous replication is a result of which property of DNA?
Antiparallel nucleotide strands
Primers are synthesized where on the lagging strand?
At the beginning of every okazaki fragment
Which bacterial enzyme removes the primers?
DNA polymerase l
In comparison with prokaryotes, what are some differences in the genome structure of eukaryotic cells that affect how replication takes place?
The size of eukaryotic genomes, the linear structure of eukaryotic chromosomes, and the association of DNA with histone proteins
What would be the result if an organism’s telomerase were mutated and nonfunctional?
Chromosomes would shorten every generation