In the first of the sequence of three lectures, I will provide a high level overview of biological processes and systems, and associated modeling techniques. In particular, I will describe sequence based modeling, sequence analysis techniques, and their applications. In this context, I will discuss a number of basic information theoretic concepts. Building on these basic concepts, I will discuss the structure and role of genetic machinery, protein interactions, and signaling cascades. I will describe various formalisms used to model these datasets, along with algorithmic and statistical issues. The lecture provides the basis for the next two lectures, discussing methods and models for analyzing interaction data and sequencing.