The genotype refers to the "internally coded, inheritable information" carried by all living organisms. This information is stored in the genome within almost all cells (internal), it is copied at the time of cell division or reproduction and is passed from one generation to the next (inherited). This information controls the formation of protein macromolecules, the regulation of metabolism and synthesis, etc.
Human genomes consist of 23 chromosome pairs in the cell nucleus and a small DNA molecule within the mitochondrion. The haploid human genome (contained in egg and sperm cells) consists of three billion DNA base pairs, while the diploid genome (found in somatic cells) has twice the DNA content. The haploid human genome contains approximately 20,000 protein-coding genes. These protein-coding sequences account for only a very small fraction of the genome (approximately 1.5%), the rest is associated with non-coding RNA molecules, regulatory DNA sequences, introns, and sequences to which no function has yet been assigned.
Each person’s genome differs in terms of single nucleotide polymorphisms (SNPs), as well as structural variations (deletions, duplications, insertions, etc.). More than 38 million SNPs, 1.4 million short insertions and deletions, and 14,000 larger deletions have now been identified. These variations are an important source of biochemical, metabolic and phenotypic diversity among individuals and populations. However, some of these genomic variations are known to cause rare genetic disorders; others are important factors in susceptibility to common diseases, including cancer, diabetes, heart disease, etc.