Final answer:
Strains of mice specifically engineered to have one or more genes inactivated are known as Knockout mice (C). They are a fundamental research tool to study gene function through reverse genetics by observing the changes that occur following gene inactivation.
Step-by-step explanation:
Strains of mice that have been developed to investigate the consequences of the inactivation of specific, targeted genes are called C) Knockout mice. These mice are genetically engineered so that one or more of their genes have been turned off, or 'knocked out,' to study the role of that gene in normal physiology and development.
For instance, in one experiment, Hfr cells containing functional A, B, C, D genes were mated with recipient cells containing mutants of either the A, B, C, or D gene. This type of genetic manipulation helps researchers understand the inheritance patterns and functions of specific genes. Additionally, the use of reporter genes, such as the one that encodes for green fluorescent protein (GFP), allows researchers to easily identify and track the expression of genes of interest in transgenic animals.