Questions:

1. SSB proteins bind to single-stranded DNA at the replication fork and prevent the formation of short hairpin helices thatwould otherwise impede DNA synthesis. What sorts of sequences in single-stranded DNA might be able to form ahairpin helix? Write out an example of a sequence that could form a 5-nucleotide hairpin helix, and show the helix.

2. One remarkable feature of the genetic code is that amino acids with similar chemical properties often have similar codons.Codons with U or C as the second nucleotide, for example, tend to specify hydrophobic amino acids. Can you suggest apossible explanation for this phenomenon in terms of the early evolution of the protein synthesis machinery?

3. (True/False) When read in the same direction (5′ to 3′), the sequence of nucleotides in a newly synthesized DNA strand isthe same as in the parental template strand. Explain your answer.