The pa of the gene which is retained in the mature mRNA is:

Exons RNA sequences that appear in mature RNAs . In mRNA encoding genes exons are often interrupted by long sequences of DNA that neither appear in mature mRNA, nor contribute to the genetic information ultimately translated into the amino acid sequence of a protein molecule. Introns Intervening sequences are called as introns, Intron less genes: Interferon genes Histone genes Many ribonuclease genes Heat shock protein genes Many G-protein coupled receptors