The human genome is made up of 3.1 billion nucleotide pairs arranged linearly in chromosomes. Human cells are diploid, that is, there are two complete sets of chromosomes (23 pairs of autosomes and two sex chromosomes), one originating from each parent.
There are 23000-25000 genes: these comprise directly transcribed sequence (exons and untranslated regions) 1.9% of the genome, and intronic DNA (36% of genome). Approximately 5% of the genome is segmental duplications.