BIOL1020 Study Guide - Taq Polymerase, Dna Polymerase Iii Holoenzyme, Thermus Aquaticus
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Document Summary
Dna exists as a helix of two antiparallel strands which interact through weak hydrogen bonds. Have direction due to 3" and 5". 5" end has a phosphate group where 3" has an oh group. Dna consists of four subunits: a,c, g & t. Adenine and guanine = purines (two carbon-nitrogen rings) Cytosine, thymine and uracil = pyrimidines (one carbon-nitrogen ring) Both sugars are pentose sugars with 5 carbon atoms. Human chromosome may contain 50 to 250 million base pairs. To fit into nucleus the chromosome must be 10,000 times smaller. Dna associated with basic (positively charged) proteins (the histones) which form protein-dna complexes known as nucleosomes. Contains 200 nucleotides with other histones (proteins) (linked by histone h1) Interaction between histones" positive charge and negative charge of dna. Wound into solenoid-like structure with 6 nucleosomes per turn. Chromatin fibre packed into loops attached at intervals to a scaffold of protein.
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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. |