8 13 determine the percentage of all the bases in

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Unformatted text preview: ercentage of all the bases in double-stranded DNA that is 20% thymine. [T] = 20%, so [A] = 20%. The remaining 60% is equally divided by [G] and [C], so each is 30%. 14. The composition (in mole-fraction) of one of the strands of a double-helical DNA molecule is [A]=0.20, [T]=0.40 and [G]=0.24. What can you say about [C] in the same strand? What can you say about the base composition in the complementary strand? The [C] is 0.16 in the same strand. The composition in the complementary strand is [A]=0.40, [T]=0.20, [G]=0.16, and [C]=0.24. [in mole-fraction] 15. Assuming that the two double-stranded DNA molecules in Q13 and Q14 are with the same length, which one of them has higher melting temperature? Why? The DNA in Q13 is 40% in A/T pairing, and the A/T pairing in the DNA in Q14 is 60%. Since A/T pairing has only two H-bonds (vs 3 H-bonds for G/C pairing), it takes lower temperature to dissociate the Q14 DNA than Q13 DNA. Hence, the Q13 DNA has higher meting temperature. 16. The bacterial virus M13 has a DNA genome that does not obey ‘Chargaff’s rules.’ Can you provide an explanation for this observation? The M13 genome is a single stranded DNA. It is not a complementary double-stranded DNA, thus no A/T and G/C pairings, hence does not follow the “Chargaff’s rules” 17. In your research project, you are given a single stranded DNA with the sequence of 5’-GACATCGCCCCTTTTCGATGTC-3’. You are asked to design a singlestranded DNA that is complementary to the one given to you. Write down the sequence of your design from 5’ to 3’ 5’-GACATCGAAAAGGGGCGATGTC-3’ 18. After receiving the DNA you have designed, you put these two DNA samples in the same solution, heat them up, and then gradually let the solution cool off to allow the two complementary strands to find each other so that double-stranded DNA is formed (the “annealing” process). What would happen to these DNAs if their concentrations in the solution are very low? If the concentrations of these DNAs are very low, they tend to anneal (forming complementary double strands) with itself (intramolecular hybrid) like the following diagram. 9 [Note: The complementary strand has similar situation.] 19. Suppose that you want to radioactively label DNA but not RNA in dividing and growing bacterial cells, which radioactive molecule would you add to the culture medium? Labeled thymidine or thymine. {Deoxyribose is not the best choice because it could be converted to ribose} 20. Shown below is an illustrator's rendition of a part of a single-stranded DNA structure; only two nucleotide units are shown. Unfortunately, the illustrator made two major mistakes. 1) Circle (solid line) the mistakes on the diagram and explain, 2) Label the 5’ and 3’ ends, and 3) circle (dashed line) the structure of pyrimidine. Mistake 1: Phosphate should be linked to 3’ C on deoxyribose, not 2’C Mistake 2: The 2’C on desoxyribose should not have an OH group because it is a deoxyribose. 10 11...
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This note was uploaded on 01/26/2014 for the course BIO 2960 taught by Professor Hafer during the Spring '12 term at University of Illinois, Urbana Champaign.

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