Chapter all: DNA Chromosomes Genomes
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BIO120H1 Full Course Notes
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Watson and francis crick: dna is a polymer which consists of two polynucleotide chains composed of subunits of 4 distinct types. There can be 4 possible bases attached to the sugar- phosphate complex of a dna nucleotide: adenine (a), guanine (g), They are all covalently linked through repetitive backbone of sugars-phosphate, resembling a necklace with beads. In scientific literature the nucleotides are usually referred to by the first letter. i. e. a, g, t, c. their sequence can be read similar to a text on a page: dna strands have polarity. One end of a dna strand has an 3phosphate atom. Genome specifies all the rna and amino acid sequences that the given organism can potentially synthesize. Nucleus: nucleus is a feature of eukaryotic cells. It main function is containing and protecting dna of the cells and the chemical machinery involved in gene expression.
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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. |