1.The DNA in a bacterium is uniformly labeled with 15N, and the organism shifted
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Question
1.The DNA in a bacterium is uniformly labeled with 15N, and the organism shifted to a growth medium containing 14N-labeled DNA precursors. After two generations of growth, the DNA is isolated and is subjected to density-gradient equilibrium sedimentation. What proportion of light-density DNA to intermediate-density DNA would you expect to find?
2. You are given two solutions containing different purified DNAs. One is from the bacterium P. aeruginosa and has a G + C composition of 68%, whereas tje other is from a mammal and has a G + C composition of 42.5%
a. You measure the absorbance of ultraviolet light of each solution as a function of increasing temperature. Which solution will yield the higher Tm value and why?
b. After melting the two solutions, mixing them together, and allowing them to cool, what would you expect to happen?
3. What is the sequence of the mRNA that will be synthesized from a template strand of DNA having the following sequence? 5' ACGTTACCTAGTTGC 3'
Explanation / Answer
out of the four products,3 will be 14-14N and 1 will be 14-15N in replication cycle 3. REPLICATION CYCLE 2 will consist of 2 products, 1 will be 14-14N and another one will be 15-14N or intermediate density.
ques2.The Tm is defined as the temperature in degress Celsius, at which 50% of all molecules of a given DNA sequence are hybridized into a double strand, and 50% are present as single strands.G-C bond is stronger than the A-T bond. higher GC content will take more time to become single stranded ,hence higher Tm.
ques 3. the sequence of the mrna will be 5-ACGUUACCUAGUUGC-3
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