Question

13. Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? 14. What produces the directionality of the DNA molecule? 15. Draw the monomer that makes up a DNA polynucleotide. 16. Describe the "backbone" of DNA. What makes up the backbone and how are the units joined together? 17. What is the difference between a nucleotide and a nucleoside? Draw each. 18. Draw each of the nitrogenous bases found in DNA and RNA. On each drawing, indicate where the base would bind to another nitrogenous base. Also, on each, indicate where the base would bind to the backbone. 19. DNase is an enzyme that catalyzes the hydrolysis of covalent bonds in DNA. Describe what would first happen to DNA molecules treated with DNase? 20. Chargaff collected data on the propostions of different organisms and tissues. Data from the DNA analyzed are present below: a. For each organism, compute the ratio of (A+G)/(T+C) AND the ratio of (A+T)/(C+G) b. Are these ratios constant or do they vary among the organisms? Explain your answer for EACH ratio. Organism/Tissue %A %G %C %T Sheep thymus 29.3 21.4 21.0 28.3 Pig liver 29.4 20.5 20.5 29.7 Human tissue 30.9 19.9 19.8 29.4 Rat bone marrow 28.6 21.4 20.4 28.4 Hen erythrocytes 28.8 20.5 21.5 29.2 Yeast 31.7 18.3 17.4 32.6 Bacteria (E. coli) 26.0 24.9 25.2 23.9

          13. Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
14. What produces the directionality of the DNA molecule?
15. Draw the monomer that makes up a DNA polynucleotide.
16. Describe the "backbone" of DNA. What makes up the backbone and how are the units joined together?
17. What is the difference between a nucleotide and a nucleoside? Draw each.
18. Draw each of the nitrogenous bases found in DNA and RNA. On each drawing, indicate where the base would bind to another nitrogenous base. Also, on each, indicate where the base would bind to the backbone.
19. DNase is an enzyme that catalyzes the hydrolysis of covalent bonds in DNA. Describe what would first happen to DNA molecules treated with DNase?
20. Chargaff collected data on the propostions of different organisms and tissues. Data from the DNA analyzed are present below:
a. For each organism, compute the ratio of (A+G)/(T+C) AND the ratio of (A+T)/(C+G)
b. Are these ratios constant or do they vary among the organisms? Explain your answer for EACH ratio.

Organism/Tissue %A %G %C %T
Sheep thymus 29.3 21.4 21.0 28.3
Pig liver 29.4 20.5 20.5 29.7
Human tissue 30.9 19.9 19.8 29.4
Rat bone marrow 28.6 21.4 20.4 28.4
Hen erythrocytes 28.8 20.5 21.5 29.2
Yeast 31.7 18.3 17.4 32.6
Bacteria (E. coli) 26.0 24.9 25.2 23.9

13. Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
14. What produces the directionality of the DNA molecule?
15. Draw the monomer that makes up a DNA polynucleotide.
16. Describe the "backbone" of DNA. What makes up the backbone and how are the units joined together?
17. What is the difference between a nucleotide and a nucleoside? Draw each.
18. Draw each of the nitrogenous bases found in DNA and RNA. On each drawing, indicate where the base would bind to another nitrogenous base. Also, on each, indicate where the base would bind to the backbone.
19. DNase is an enzyme that catalyzes the hydrolysis of covalent bonds in DNA. Describe what would first happen to DNA molecules treated with DNase?
20. Chargaff collected data on the propostions of different organisms and tissues. Data from the DNA analyzed are present below:
a. For each organism, compute the ratio of (A+G)/(T+C) AND the ratio of (A+T)/(C+G)
b. Are these ratios constant or do they vary among the organisms? Explain your answer for EACH ratio.

Organism/Tissue %A %G %C %T
Sheep thymus 29.3 21.4 21.0 28.3
Pig liver 29.4 20.5 20.5 29.7
Human tissue 30.9 19.9 19.8 29.4
Rat bone marrow 28.6 21.4 20.4 28.4
Hen erythrocytes 28.8 20.5 21.5 29.2
Yeast 31.7 18.3 17.4 32.6
Bacteria (E. coli) 26.0 24.9 25.2 23.9

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