ABSTRACT
The chapter presents an introduction to deoxyribose nucleic acid (DNA) bases, genes and chromosomes, identifying the 46 chromosomes of the karyotype. The 22 pairs of autosomes are discussed. Each chromosome is illustrated, with the mental health–related genes identified and located. Gene alleles, gene loci, the concept of phenotype, recessive and dominant gene inheritance patterns, homozygous and heterozygous traits and penetrance are explored. Types and causes of gene mutations and disorders of autosomal mutations and abnormal chromosomal counts (trisomy and monosomy), e.g. Down syndrome, Patau syndrome, Edwards syndrome, Williams syndrome and Warkany syndrome, are discussed. The concept and consequences of mosaicisms within individual cells are explained.
