BIOL 2500 Lecture Notes - Lecture 21: Guanine, Internal Control, Thymine
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3 Apr 2017
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Once the structure of dna was known, researches began to investigate how information from. Rna was shown to be abundantly present in all cells and chemically similar to dna, but its function was unclear. Cell structure suggested a role for rna in protein synthesis (i. e dna in eukaryotic cells resides in the nucleus, while protein synthesis takes place in the cytoplasm) Rna nucleotides are composed of a sugar, nucleotide base, and one or more phosphate groups, with two critical differences compared to dna nucleotides o. The bases adenine, guanine, and cytosine are the same, but thymine is replaced by uracil o. The sugar ribose is used rather than deoxyribose. The similar sugars in rna and dna lead to formation of nearly identical sugar-phosphate backbones in the molecules. Rna strands are assembled by formation of phosphodiester bonds between the 5" phosphate of one nucleotide and the 3" hydroxyl of the adjacent one.
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Related Questions
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. |