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19 Cards in this Set
- Front
- Back
Chain Facts!
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-Antiparallel
-Basses of opposite chains are paired:A-T, C-G -Hydrogen bonds connecting bases -bases are flat, lie perpendicular to axis, and stack |
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Basepairing provides:
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Complimentarity of the two strands and chemical stability to the helix
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Hydrogen bonding between bases
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A-T base pairs form two hydrogen bonds and G-C base pairs form three hydrogen bonds
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Other DNA structures:
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-A-DNA-slightly more compact than
B-DNA.
-B-DNA-believed to be the biologically significant form -C,D,E-DNA-right-handed forms of DNA that are less compact than B-DNA. |
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RNA FACTS!
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-Similar to DNA, but single Stranded
-Sub Ribose instead of Deoxyribose -Sub U for T -some RNAs form double-stranded regions as they fold into different secondary structures |
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three classes of cellular RNAs
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-messenger RNA (mRNA): templates for protein synthesis
-ribosomal RNA (rRNA): components of ribosomes -transfer RNA (tRNA): carry amino acids for protein synthesis |
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Sedimentation:
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-Nucleic acids can be separated by gradient centrifugation procedures.
-Sedimentation equilibrium centrifugation separates by density gradient. |
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Hyperchromic shift
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during DNA denaturation is used to determine the melting temperature (Tm).
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As DNA melts (denatures):
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both the UV absorption and buoyant density increases.
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Reassociation Kinetics
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provides information about the size and complexity of genomic DNA from an organism
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In molecular Hybridization:
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DNA strands (or DNA and RNA strands) can be renatured to each other.
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Fluorescent in situ hybridization (FISH)
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is used to identifying the chromosomal location of a DNA of interest.
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Nucleic Acid ELectrophoresis
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separates DNA and RNA fragments by size such that smaller fragments migrate through a gel at a faster rate than large fragments
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Three possible modes of DNA replication
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-Conservative-seperate to replicate, then rewind with original
-Semiconservative-STR, 1 new 1 old strand -Dispersive-some old some new to both strands |
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The Meselson-Stahl experiment
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-DNA replication is semi conservative
-each new DNA molecule consists of one old strand and one newly synthesized strand |
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Taylor-Woods-Hughes experiment
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-Demonstrated semi conservative replication in eukaryotes
-Used root tips of Vicia fabia (excellent source of dividing cells) -Monitored replication by labeling with H3-thymidine (radioactive) |
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DNA Replication
BACTERIAL |
-Originates at ‘origins of replication’ in bacterial cells.
-Stands unwind during replication creating a ‘replication fork’. -Replication is bidirectional -Segment of DNA that is replicated is a ‘replicon’ – in bacteria this is the whole chromosome. |
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Bidirectional replication creates
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two replication forks
that eventually merge at a termination region (ter). |
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Bacterial DNA synthesis
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-involved 5 plymerases, and other enzymes
-Chain elongation direction:5-3, by addition of one nucleotide to 3 base end -As the nucleotide is added, the two terminal phosphates are cleaved off |