MCDB 20 Midterm: Midterm2
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11 Mar 2016
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Structure: five carbon structure (deoxyribose), a phosphate group, and a base: double helix - twisted ladder of sugar phosphate strands, connecting bases form rungs ii. Bases: adenine, always pairs with thymine, guanine, always pairs with cytosine. 2. introns - non coding regions: spliced out in mrna, many genes = chromosome iv. How genes work: transcription, recognize and bind i. Enzyme (rna polymerase) binds to dna and begins reading gene"s message: transcribe i. Rna polymerase builds a single strand rna copy of the gene: known as mrna transcript, terminate i. ii. Rna polymerase encounters a code telling it to stop transcription stops and the mrna transcript is released: cap and process i. In eukaryotes: mrna"s receive extra processing: cap and tail added for protection and to promote recognition, non-coding sections (introns) are removed, translation - uses information from mrna to create proteins a. Ingredients needed in the cytoplasm: i. ii. iii.
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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. |