There are three types of genetic disorders: 1  Single-gene disorders, where a mutation affects one gene. Sickle cell anemia is an example. 2  Chromosomal disorders, where chromosomes (or parts of chromosomes) are missing or changed. Chromosomes are the structures that hold our genes. 3  Complex disorders, where there are mutations in two or more genes.
OSI model. The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard protocols.
OSI Model. 1  The Physical Layer (Layer 1) 2  The Data Link Layer (Layer 2) 3  The Network Layer (Layer 3) 4  The Transport Layer (Layer 4) 5  The Session Layer (Layer 5) 6  The Presentation Layer (Layer 6) 7  The Application Layer (Layer 7)