The GenPak (GP) package contains many command-line utilities which 
fullfill a whole bunch of tasks, from DNA sequence searches to 
restriction analysis and determining the melting temperature of 
oligonucleotides. GP utilities can convert DNA / RNA to protein, 
determine codon usage / GC contents, do promotor searches, calculate 
Tm, search for restriction sites, convert sequences into numerical 
representations and much more.

You most likely want to install Arka, which provides a GUI for GenPak.