ABSTRACT
Hereditary details are contained in the genes located in every cell of the body. Many genes display various types of 'incomplete' dominance and co-dominance. Most characteristics, particularly the psychosocial features at work in relationships, emotion and behaviour, involve the operation of numerous genes in complex interactions with each other. An additional source of variation occurs because genetic information is occasionally not passed accurately through the generations. Twenty-two of the chromosomal pairs are similar for males and females. Chromosome 23 is an exception, and it controls sex. There are a number of research designs which attempt to examine the relative contributions of genes and environment. Adoption studies examine whether adopted children are more similar to their birth parents or their adoptive parents. Population genetics, using the techniques of molecular biology, compare the genetic makeup of 'populations' with and without a particular characteristic, and have generally been most effective in medical genetics rather than behavioural genetics.
