HW 1-7 NUCLEIC ACIDS

Figure 5.28 DNA RNA  protein: a diagrammatic overview of information flow in a cell

Figure 5.29 The components of nucleic acids Link to ribose

ON TEST

RNA as single-stranded molecules; RNA self-complementary hairpin loop structures t-RNA

ON TEST – BE ABLE TO DRAW 5

ON TEST – BE ABLE TO DRAW Solid Line = Covalent Bond Dotted or dashed line = hydrogen bonds

Figure 16.5 The double helix Link to DNA structure animation advanced

Regulatory Proteins Often Bind to specific sequences in the Major Groove of DNA

Figure 16.6 Base pairing in DNA

Figure 5.30 The DNA double helix and its replication

Thought Question (30 sec thought time, then discuss with a partner) Explain the following observation: At physiological pH, (≈ 7), DNA is water soluble. When a 10% solution of trichloroacetic acid (TCA)is added to a solution of DNA, DNA that contains 20 or more nucleotides precipitates out of solution. Using what you learned in the hydrophilic/ hydrophobic lab and from our discussion of DNA structure, propose an explanation for this observation. Structure of TCA

Possible Answer: Trichloroacetic acid contains an acidic carboxylic acid group. It will donate a proton to the negatively charged oxygens on the phosphate groups of the DNA backbone, neutralizing the negative charge. Without the full charges on the O’s the attraction for water will be greatly reduced and for large polymers the neutral DNA will come out of solution.