1. Formaldehyde reacts with amino groups to form hydroxymethyl derivatives. A) W
ID: 55361 • Letter: 1
Question
1. Formaldehyde reacts with amino groups to form hydroxymethyl derivatives. A) Would you expect formaldehyde to react with bases in DNA? Suppose you have a solution that contains separated complimentary strands of DNA. B) would the addition of formaldihyde to the solution affect reassociation of the strands?
2.In contrast to DNA polymerae, RNA polymerase has no nuclease capability to excise mismatched nucleotides. Suggest why the two enzymes are different in this respect.
3.You are studying the effects of amino acid replacements on the stability of a particular alpha-helix that is buried in the protein myoglobin. You carry out a site-specific mutagenesis. The replacements you make are as follows: Leu->Arg, Leu-> Val, Leu->Pro, Leu->Gly, Leu_>Ala
a.For each replacement, predict whether the change would stabilize, destabalize, or have no effect on the structure of the alpha-helix. Briefly explain each of you predictions.
b. For each replacement, write the most likely mRNA codon required to code for that particular amino acid substitution. Which of the replacement can be carried out by single-base changes? Which of the replacements can be produced only by altering two bases in the mRNA codon?
C.
Substitution Effect Prediction Prediction explanation Codon # of changes Leu->Arg Leu->Val Leu->Pro Leu->Gly Leu->AlaExplanation / Answer
A. It reacts with the bases of dna, it crosslinks the Dna. it reacts reversibly with nucleic monomer,capable of reacting reversibly.B it cannot cause reassociation,because its a denaturant
2. rna polymerase has no proof reading activity i.e the 3'to 5' activity,hence it cannot remove the bases.
3
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