BIOL 4087 : BIOCHEMISTRY TEST 2 NOTES
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Nucleoside = base + sugar: for purines sugar attaches to base at the number 9 spot (figure 8-4) Phosphodiester bond (dna)(rna) the 3" to 5" link between nucleotides in dna and rna. If sequence is not specified far most left side is 5" end. Watson-crick structure of dna: double stranded, strands are antiparallel and are complimentary, a=t both base pairs have 2 hydrogen bonds. G=c both base pairs have 3 hydrogen bonds: double helix bases are more hydrophobic therefore on inside and sugars and phosphate are on outside more hydrophilic. Major and minor grooves: bases are accessible to dna binding proteins. B form dna in solution (watson-crick) double stranded dna (dsdna) A form rna dna hybrids or double stranded rna (broader helix) Dna replication is present in each of the two daughter strands. Nick translation carried out by dna polymerase i 5" 3" exonuclease (figure 25-16: termination.
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QUESTION 1. Compared to eukaryotic genomes, only prokaryotic genomes:
A. contain DNA organized by histones. |
B. contain usually one, circular chromosome. |
C. contain plasmid DNA. |
D. have chromosomes contained in a nucleus. |
QUESTION 2. Azathioprine is a drug that may be prescribed to transplant recipients to reduce the chance of tissue rejection reactions. In its active state, it acts as a purine analogue, inhibiting DNA biosynthesis. This means that 6-mercaptopurine will be inserted in place of a purine containing nucleotides during DNA replication. Given this drug's mode of action, you would expect it to be incorporated into DNA in place of:
A. nucleotides containing guanine or cytosine. |
B. nucleotides containing adenine or thymine. |
C nucleotides containing adenine or guanine. |
D. nucleotides containing guanine nucleotide or uracil. |
QUESTION 3. RNA is distinguished from DNA because only RNA:
A. typically exists as a single-stranded molecule. |
B. has a 3' to 5' directionality. |
C. is composed of nucleotides that contain the sugar deoxyribose. |
D. is composed of nucleotides that contain the nitrogen bases T, C, G, and A. |
QUESTION 4. How are RNA nucleotides different from DNA nucleotides? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer.
A. RNA nucleotides do not contain thymine. |
B. RNA nucleotides use the sugar ribose, while DNA nucleotides do not. |
C. RNA nucleotides lack phosphate. |
D. RNA nucleotides incorporate pyrimidine nitrogen bases, while DNA nucleotides only incorporate purine nitrogen bases. |