Behavior largely depends on multiple genes, but not completely. The genotype does not determine behavior only, but rather the general principles for constructing neural circuits responsible for processing incoming information and making decisions. These mechanisms are capable of learning and are constantly rebuilt throughout life.
The methodology for studying the effects of multiple genes on behavior involves observation and experiment. Observing the behavior of the creatures in the habitual conditions supplemented by the events of their occasions with various objects. The experimental method is considered more illustrative. Transgenesis can be used to examine the influence of multiple genes on behavior. The methodology of using transgenic animals is called transgenesis. The transgenic subject of study is placed in certain conditions with additional stimuli and based on its actions and reactions, the influence of genes on behavior can be researched.
An experimental method needs a suitable test subject. Transgenic animals with changed genomes as a result of various operations are commonly used in research for this purpose. In the most general form, transgenesis can be defined as the transfer of genes from one organism to another through in vitro operations. The three critical points in transgenesis are the integration of the transgene, its expression, and transmission, i.e. transmission through germ cells to offspring. Transgenesis is a strategic direction of research that provides answers to numerous fundamental questions, finding its application in the study of the functioning of gene activity regulation systems, in the fields of immunology, embryogenesis, development of the nervous system, mechanisms of hematopoiesis and angiogenesis, studies of factors that regulate the growth and differentiation of multipotent stem cells and, finally, in the field of carcinogenesis.