Term
| Semiconservative Replication |
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Definition
| One old and one new DNA strand on both helices. All DNA replication is semiconservative. |
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Term
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Definition
| Individual units of replication. Bacteria and viruses with one origin of replication have 1 replicon. Eukaryotic chromosomes with many origins have many replicons. |
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Term
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Definition
Both strands old DNA on one helix.
Both strands new DNA on one helix.
After one round of replication, 50% of the molecules consits of the original DNA and 50% of new DNA. After two rounds, 25% of the molecules consists of the original DNA and 75% of new new DNA. THe proportion of molecules with new DNA increase with each additional round of replication. The original DNA is constant. |
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Term
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Definition
| Old & new DNA mixed on both strands on both helices. None of the original molecule is conserved. Always produces hybrid molecules but the proportion of new DNA increases with each replication. |
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Term
Meselson and Stahl's Experiment
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Definition
| Determined which of the three models of replication applied to E. coli cells. Did so by using two isotopes of nitrogen. Grew a culture of E. coli in a medium that contained 15N as the sole nitrogen source; after many generations, all the E coli cells had 15N incorporated into the purine and pyrimidine bases of DNA. They took a sample of these bacteria, switched the rest of the bacteria to a medium that contained only 14N, and then took additional samples of bacteria over the next few cellular generations. In each sample, the bacterial DNA that was synthesized before the change in medium contained 15N and was relatively heavy, whereas DNA synthesized after the switch contained 14N and was relatively light. Distinguished between heavy and light with the use of equilibrium density gradient centrifugation |
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Term
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Definition
| Type of repication taking place in circular DNA (E. coli). Is uni or bidirectional; replication at both ends of a replication bubble. Products are 2 circular DNA. |
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Term
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Definition
| = 2000 base pairs/ 1 second |
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Term
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Definition
| The point of unwinding, where the two single nucleotide strands separate from the double-stranded DNA helix. |
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Term
| Rolling Circle Replication |
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Definition
| Occurs in small circular genomes including small viruses. Replication is initiated by a break in one of the nucleotide strands. DNA synthesis begins at the 3' end of the broken strand; the inner strand is used a stemplate. The 5' end of the broken strand is displaced. Cleavage releases a single-stranged linear DNA and a double-stranded circular DNA. The linear DNA may circularize and serve as template for synthesis of a complementary strand. The products are multiple circular DNA molecules. Is Unidirectional. |
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Term
| Linear Eukaryotic Replication |
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Definition
| Slower than bacterial replication because the large lienar chromosomes in eukaryotic cells contain far too much DNA to be replicated speedily from a single origin. Each chromosome contaisn numerous origins. At each origin, the DNA unwinds, producing a replication buble. DNA synthesis takes place on both strands at each end of the buble as teh replication forks proceed outward. Eventually, the forks of adjacent bubbles run into each other and the segments of DNA fuse, producing two identical linear DNA molcules. Is Bidirectional and has many replicaons. |
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Term
| Requirements of Replication |
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Definition
1. A template consisting of single-stranded DNA
2. raw materials (substrates) to be assembled into a new nucleotide strand
3. enzymes and other proteins that "read" the template and assemble the substrates into a DNA molecule. |
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Term
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Definition
| The enzymes that synthesize DNA, can add nucleotides only to the 3' end of the growing strand, and so new DNA strands always elongate in the same 5'-3' direction. |
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Term
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Definition
| 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. |
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Term
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Definition
| DNA strand that is replicated continuously |
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Term
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Definition
| DNA strand that is replicated discountinuously |
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Term
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Definition
| Short stretch of newly synthesized DNA. Produced by discontinuous replication on the lagging strand, these fragments are eventually joined together. |
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Term
| Discontinuous Replication |
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Definition
| Replication of the lagging strand in the direction opposite that of unwinding, which means DNA must synthesize in short stretches (Okazaki fragments). |
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Term
| Four stages of replication |
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Definition
1. Initiation
2. Unwinding
3. Elongation
4. Termination |
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Term
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Definition
| The circular chromosome of E. coli has a single replication of origin (oriC). The minimal sequence required for oriC to function consists of 245 bp that contain several critical sites. An initiator protein (DnaA in E. coli) binds to oriC and causes a short section of DNA to unwind. This unwinding allows helicase and other single-strand-binding proteins to attach to the polynucleotide strand. |
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Term
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Definition
| Because DNA synthesis requires a single-stranded template and because double-stranded DNA must be unwound before DNA synthesis can take place, the cell relies on several proteins and enzymes to accomplish the unwinding. |
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Term
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Definition
| Protein that unwinds double-stranded DNA by breaking hydrogen bonds. Cannot initiate unwinding of double-stranded DNA; the initator protein first separates DNA strands at the origin, providing a short stretch of single-stranded DNA to which a helicase binds. Binds to the lagging-strand template at each replication fork and moves in the 5'-3' direction along this strand, thus also moving the replication fork. Uses ATP to unwind DNA |
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Term
| Single-stranded binding proteins (SSBs) |
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Definition
| Attach tightly to the exposed single-stranded DNA. Will bind to any single-stranded DNA in replication and prevents it from annealing (recombining) with a complementary strand and forming secondary structures. SSBs form tetramers; each covering from 35 to 65 nucleotides. Keeps the helix open so replication can occur. |
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Term
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Definition
| A topoisomerase enzyme that relives the tosional strain that buidls up ahead of the replication fork. It reduces torque by making a double-stranded break in one segment of the DNA helix, passing another segment of the helix through the break, then resealing the broken ends of DNA. This action removes a twist in the DNA and reduces the supercoiling. |
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Term
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Definition
| Short stretch of RNA on a DNA template; provides a 3' OH group for the attachment of a DNA nucleotide at the initation of replication. Are synthesized at the beginning of every Okazaki fragment. |
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Term
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Definition
| After DNA is unwound and a primer has been added, DNA polymerases elongate the polynucleotide strand by catalyzing DNA polymerization. |
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Term
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Definition
| Enzymes that cleave the phospodiester bonds so the helix can swing around as it unwinds. |
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Term
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Definition
| Allows transient breaks in one strand of the helix so that hte unwinding by DNA helicase can happen quickly. Breaks and reforms the phospodiester bond on one strand. Does not require ATP. |
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Term
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Definition
| Breaks and reforms the phospodiester bonds on two strands at once. This requires ATP. DNA gyrase is the best known topo II enzyme. |
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Term
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Definition
| Synthesizes a short RNA complementary to a specific DNA region. Usually found in a multienzyme complex, the primosome. |
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Term
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Definition
Has 5'->3' polymerization
Has 3'->5' Exonuclease
Has 5'->3' Exonuclease
Removes and replaces primers |
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Term
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Definition
Has 5'->3' polymerization
Has 3'->5' Exonuclease
Does not have 5'->3' Exonuclease
DNA repair; restarts replication after damaged DNA halts synthesis
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Term
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Definition
Has 5'->3' polymerization
Has 3'->5' Exonuclease
Does not have 5'->3' Exonuclease
Elongates DNA |
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Term
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Definition
Has 5'->3' polymerization
Does not have 3'->5' Exonuclease
Does not have 5'->3' Exonuclease
DNA repair |
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Term
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Definition
Has 5'->3' polymerization
Does not have 3'->5' Exonuclease
Does not have 5'->3' Exonuclease
DNA repair; translesion DNA synthesis |
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Term
| All of E coli's DNA Polymerases: |
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Definition
1. Synthesize any sequence specified by the template strand
2. Synthesize in the 5'->3' direction by adding nucleotides to a 3'-OH group
3. Use dNTPs to synthesize new DNA
4. require a primer to initiate synthesis
5. Catalyze the formation of a phosphodiester bond by joining the 5' phosphate group of the incoming nulceotide to the 3'-OH group of the preceding nucleotide on the growing strand, cleaving off two phosphates in the process
6. Produce newly synthesized strands that are complementary and antiparallel to the template strands
7. are associated with a number of other proteins. |
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Term
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Definition
| Enzyme that catalyzes the formation of a phosphodiester bond between adjacent 3'-OH and 5' phosphate groups in a DNA molecule. |
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Term
| Five requirements of Replication Fork |
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Definition
1. Helicase to unwind the DNA
2. SSBs to keep the nucleotide strands separate long enough to allow replication.
3. The topoisomerase gyrase to remove strain ahead of the replication fork.
4. Primase to synthesize primers with a 3'-OH group at the beginning of each DNA fragment
5. DNA polymerase to synthesize the leading and lagging nucleotide strands. |
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Term
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Definition
| Replication is terminated whenever two replication forks meet. A terminator protein, called Tus in E. coli, binds to these sequences. Tus blocks the movement of helicase, thus stalling the replication for and preventing further DNA replication. |
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Term
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Definition
Has 5'->3' Polymerase Activity
Does not have 3'->5' Exonuclease activity
Initiation of nuclear DNA synthesis and DNA repair; has primase activity. |
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Term
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Definition
Has 5'->3' Polymerase Activity
Has 3'->5' Exonuclease activity
Leading and lagging strand synthesis of nuclear DNA, DNA repair, and translesion DNA synthesis |
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Term
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Definition
Has 5'->3' Polymerase Activity
Has 3'->5' Exonuclease activity
Leading strand synthesis |
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Term
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Definition
| Enzyme with both a protein and an RNA component. Behaves as reverse transcriptase synthesizing a DNA complement (strand) on an RNA template. aka ribonucleoprotein. |
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