Practice question

Human mitochondrial DNA is a circular, 16.6 kb molecule inherited maternally, lacking introns and histones, encoding components of oxidative phosphorylation system. Initial complete sequencing by Anderson et al. revealed 37 genes: 13 protein coding for subunits of respiratory complexes I, III, IV and V, 22 transfer RNAs and 2 ribosomal RNAs 12S and 16S. Non-coding D-loop regulates replication and transcription. Compact organization with overlapping genes and minimal intergenic spacers maximizes coding capacity. Counting only protein genes yields 13, but total gene number including RNAs is 37.