1) The semiconservative nature of DNA replication (as shown inFig. 3.9) was proposed by Watson and Crick in 1953, but it wasn'texperimentally verified until 1958. Meselson and Stahl grewbacteria on the âheavyâ nitrogen isotope N15, producing DNA thatwas denser than normal. The food source was then abruptly switchedto one containing only N14. Bacteria were harvested and the DNAisolated by density gradient centrifugation.
a.
What is the density of the DNA of the first-generation daughterDNA molecules? Explain.
b.
What is the density of the DNA isolated after two generations?Explain.
c.
What results would Meselson and Stahl have obtained had DNAreplicated conservatively?
2) a. One form of the diseaseadrenoleukodystrophy (ALD) is caused by the substitution of serinefor asparagine in the ALD protein. List the possiblesingle-nucleotide alterations in the DNA of the ALD gene that couldcause this genetic disease. b. In another form ofALD, a CGA codon is converted to a UGA codon. Explain how thismutation affects the ALD protein.
1) The semiconservative nature of DNA replication (as shown inFig. 3.9) was proposed by Watson and Crick in 1953, but it wasn'texperimentally verified until 1958. Meselson and Stahl grewbacteria on the âheavyâ nitrogen isotope N15, producing DNA thatwas denser than normal. The food source was then abruptly switchedto one containing only N14. Bacteria were harvested and the DNAisolated by density gradient centrifugation.
a.
What is the density of the DNA of the first-generation daughterDNA molecules? Explain.
b.
What is the density of the DNA isolated after two generations?Explain.
c.
What results would Meselson and Stahl have obtained had DNAreplicated conservatively?
2) a. One form of the diseaseadrenoleukodystrophy (ALD) is caused by the substitution of serinefor asparagine in the ALD protein. List the possiblesingle-nucleotide alterations in the DNA of the ALD gene that couldcause this genetic disease. b. In another form ofALD, a CGA codon is converted to a UGA codon. Explain how thismutation affects the ALD protein.
