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Morgan.liberatore
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What charge does a phosphate group have a neutral pH?
Negatively charged
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Where is the phosphate group attached to a nucleotide?
Attached to C5' position on the ribose (pentose) ring
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How many phosphate groups do nuleic acids contain?
Nucleic acids contain one phosphate group per nucleotids
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What is Pentose?
A five-carbon sugar
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What is deoxyribose?
A pentose molecule with no O atom on carbon 2'
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Why are carbon atoms in pentose numbered with primes?
Has carbon atoms numbered with primes to distinguish them from the atoms in nitrogen bases
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What are nucleobases?
Derivatives of pyrimidine or purine
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Are nucleo bases planar?
yes, they are planar or almost planar structures
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What kind of light do nucleobases absorb?
Absorb UV light around 250-270nm
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What is the general structure of a nucleobase?
Nitrogen-containing heteroaromatic molecules
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In all nucleotides, where is the phosphate group located?
At the 5' position
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What is the backbone of DNA/RNA made of?
Alternating phosphate and sugar groups
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As a rule, how are DNA/RNA polymers written?
From 5' to 3'
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How are nucleosides in DNA/RNA polymers linked?
By a phospho-diester linkage
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Which end of the DNA/RNA poymers are phosphorylated?
5'
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What are DNA/RNA polymers less than 50 nucleotides refered to as?
Oligonucleotides
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What are DNA/RNA polymers sensitive to?
Alkaline hydrolysis
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Which is more sensitive to Alkaline hydrolysis, DNA or RNA?
RNA, due to 2' OH
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What do phosphodiester bonds do in DNA?
Link successive nucleotide units
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Why are nucleic acids highly polar?
The backbone of alternating pentose and phosphate groups
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Why are the ends named 5' and 3'?
The 5' and of the macromolecule lacks a nucleotide at the 5' position and the 3' end lacks a nucleotide at the 3' position
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What happens in RNA hydrolysis under Alkaline conditions?
- The 2' hydroxul acts as a nucleophile in an intamolecular displacement.
- The 2',3'- cyclic monophosphate derivative is further hydrolyzed to a mizture of 2'- and 3'-monophosphates
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Why is DNA stable under Alkaline conditions?
It lacks 2' hydroxyls
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What do nucleic acid polymers do?
Mediate the storage and transfer of genetic material
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What are the 3 'game-changer' experiments?
- Griffit- 'Transforming Principle'- 1928
- Avery-McLaeod-McCarty- 'DNA fractions'-1943
- Hershey and Chase- Bacteriophage- 1952
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Who discovered the 'transforming principle'?
Griffith
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What was the conclusion of the 'Transforming Principle' experiment?
A transforming material (unlikely proteins) crossed from the heat ikilled virulent S strain to the non-virulent R live strain
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What was the conclusion of Aver-McLaeod-McCarty expriment?
The transforming factor is DNA
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What is the conclusion of the Hershey and Chase experiment?
The injected material from the Bacteriophage was 32P labeled. Consequently, DNA is responsible for the storage and transferred of genetic material
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Who discovered the double helix?
James Watson and Francis Crick
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What was the key to the discoverey of the double helix?
Recognition of base pairing
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What is Chargaff's rule?
- The percentge of G+Cs and A+Ts were equal
- A+G=T+C
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How are base pairs joined?
Hydrogen bonds
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Is the double helix right-handed or left-handed?
Right-handed
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What points towards the outside of the double helix?
phosphate groups
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What is the width of the double helix?
2.0nm (20A)
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How far apart are the bases along the helix axis?
0.34 nm (3.4A)
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How long is the pitch of the helix?
3.6nm (36A)
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How many nucleotides per turn of the helix?
10.4
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What is 'Central Dogma'?
refers to the flow of information from genes to proteins
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What is the first step in the 'Central Dogma'?
DNA replication
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What were the postulated methods of DNA replication?
- Semi-conservative
- Conservative
- Dispersive
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What was the conclusion of the Meselson-Stahl experiment (1957)?
Experimental evidence confirmed that DNA replication is Semi-conservative
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Is DNA bidirectional?
yes
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What does DNA polymerase do?
Catalyze the stepwise addition of deoxyribonucleotides (5'-3')
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What are the characteristics of DNA Polymerase I?
- It has 5'-3' polymerase activity
- It has 3'-5' exonuclease activity (proof reading)
- It has 5'-3' exonuclease activity (removes added primers)
- Requires a DNA template
- It is moderately processive (dissociates after adding 20 dNTPs)
- All three activites on a single polypeptide
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What are the characteristics of DNA polymerase II?
- It has 5'-3' polymerase activity
- It has 3'-5' exonuclease activity (proof reading)
- Does NOT 5'-3' exonuclease activity
- Requires DNA template
- It is highly processice (synthesizes 1000 dNTPs/second)
- It is made up of 10 subunits
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Which enzyme is responsible for the unwinding of the DNA double helix?
DNA helicase
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What is used to keep the DNA strands separate?
Single Strand Binding proteins
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What releases the stress of the DNA unwinding through transient DNA cut and ligation?
Topoisomerase
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Which enzyme does not require a free 3'OH group to add compimerntary base pairs?
Primase
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What are Okazaki fragments?
Short DNA fragments compimentary to the lagging strang sequence
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How is the RNA primer removed?
Removed by 5'-3' exonuclease activity of DNA Polymerase I
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What enzyme joins the DNA fragments on the lagging strand?
DNA Ligase
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How can DNA be denatured?
Changes to pH or temperature?
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