Solution to PS 8 #6

a) The single strand DNA template used for DNA synthesis in vitro can form secondary structures such as hairpins.  SSB  (single strand binding protein) prevents the formation of double strands structure by binding to the single stranded template.  SSB thus renders the DNA a better substare for DNA polymerase.

b)  The yield of DNA in vitro is improved at higher temperatures because formation of secondary strucure in the template is less likely.  A temperature of 65 C is high enough to prevent  formation of secondary structure but not high enough to denature newly synthesized DNA.  DNA polymerases from bacteria that grow at high temperatures are used becuase they are active at 65 C, a temperature at which DNA polymerases from other bacteria would be inactive.


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