homework 10
10.01 What evidence suggested that the transforming principle in Griffith's experiments was really a gene or genes?
10.01 What evidence suggested that the transforming principle in Griffith's experiments was really a gene or genes?
10.02 Would 14C and 3H have been suitable radioactive tracers for the Hershey-Chase experiment Why, or why not?
10.02 Would 14C and 3H have been suitable radioactive tracers for the Hershey-Chase experiment Why, or why not?
10.03 Was the model of DNA proposed by Watson and Crick consistent or inconsistent with Chargaff's rules? Explain.
10.03 Was the model of DNA proposed by Watson and Crick consistent or inconsistent with Chargaff's rules? Explain.
10.04 A particular double-stranded DNA sample has a C+G ratio of 44%. What is the fraction of all four bases in this sample?
10.04 A particular double-stranded DNA sample has a C+G ratio of 44%. What is the fraction of all four bases in this sample?
10.05 An certain virus contains a single chromosome of double-stranded DNA with 120,000 base pairs. The percentage of cytosine bases is 18%.
10.05 An certain virus contains a single chromosome of double-stranded DNA with 120,000 base pairs. The percentage of cytosine bases is 18%.
(a) Approximately how many helical turns does each chromosome contain?
(a) Approximately how many helical turns does each chromosome contain?
(b) How long is the chromosome in micrometers?
(b) How long is the chromosome in micrometers?
(c) What is the approximate molecular weight of this DNA? (The average molecular of a nucleotide is approximately 330)
(c) What is the approximate molecular weight of this DNA? (The average molecular of a nucleotide is approximately 330)
(d) Approximately how many phosphorous atoms does a single chromosome contain?
(d) Approximately how many phosphorous atoms does a single chromosome contain?
(e) Approximately how many molecules of adenine, cytosine, guanine, and thymine would a single chromosome contain?
(e) Approximately how many molecules of adenine, cytosine, guanine, and thymine would a single chromosome contain?
10.06 Draw a short segment of DNA with at least 3 base pairs. Use the following abbreviations in your diagram: D=deoxyribose, P=phosphate, A=adenine, G=guanine, T=thymine, C=cytosine. You don't need to draw the complete structures of the nucleotides, but clearly show how the components listed above are bound together. Use solid lines for covalent bonds; dotted lines for hydrogen bonds. Also label the 3' and 5' ends of each nucleotide strand.
10.06 Draw a short segment of DNA with at least 3 base pairs. Use the following abbreviations in your diagram: D=deoxyribose, P=phosphate, A=adenine, G=guanine, T=thymine, C=cytosine. You don't need to draw the complete structures of the nucleotides, but clearly show how the components listed above are bound together. Use solid lines for covalent bonds; dotted lines for hydrogen bonds. Also label the 3' and 5' ends of each nucleotide strand.
10.07 The graphs below show the results of the analysis of two different samples of DNA (labelled A and B in the graphs). The left graph shows the change in absorbance of UV light as the DNA samples are slowly heated. The right graph shows how UV light absorbance drops when the DNA samples are first heated above their melting points and then allowed to cool. What can you conclude about theses two samples of DNA? Be sure to explain how the data support your conclusions.
10.07 The graphs below show the results of the analysis of two different samples of DNA (labelled A and B in the graphs). The left graph shows the change in absorbance of UV light as the DNA samples are slowly heated. The right graph shows how UV light absorbance drops when the DNA samples are first heated above their melting points and then allowed to cool. What can you conclude about theses two samples of DNA? Be sure to explain how the data support your conclusions.
10.08 Draw diagrams of the DNA molecules as hypothesized by the Meselson-Stahl experiment after three generations in 14N medium assuming: (a) conservative, and (b) semiconservative replication. Use solid lines for 15N-labeled DNA (old strands) and dotted lines for 14N-labeled DNA (new strands). Also diagram the number and positions of the bands of DNA as they would be expected to appear in the centrifuge tube that would arise from both possible replication methods.
10.08 Draw diagrams of the DNA molecules as hypothesized by the Meselson-Stahl experiment after three generations in 14N medium assuming: (a) conservative, and (b) semiconservative replication. Use solid lines for 15N-labeled DNA (old strands) and dotted lines for 14N-labeled DNA (new strands). Also diagram the number and positions of the bands of DNA as they would be expected to appear in the centrifuge tube that would arise from both possible replication methods.
10.09 In the DNA replication studies of Meselson and Stahl, DNA was labelled with nucleotides containing an isotope of nitrogen that is more dense than typical nitrogen. What if they had labelled the DNA with radioactive nucleotides instead. Would this have worked? Explain why or why not?
10.09 In the DNA replication studies of Meselson and Stahl, DNA was labelled with nucleotides containing an isotope of nitrogen that is more dense than typical nitrogen. What if they had labelled the DNA with radioactive nucleotides instead. Would this have worked? Explain why or why not?
10.10 Make a diagram showing how bidirectional DNA replication occurs. Mark the 5' and 3' ends of each strand of nucleotides. Also label: leading strand, lagging strand, Okasaki fragment, and RNA primer.
10.10 Make a diagram showing how bidirectional DNA replication occurs. Mark the 5' and 3' ends of each strand of nucleotides. Also label: leading strand, lagging strand, Okasaki fragment, and RNA primer.