Gene organization:

In marked contrast to prokaryotic genes where proteins are encoded through a continuous sequence of triplet codons and the vast majority of protein-coding genes in eukaryotes are discontinuous. The coding sections of the gene known as exons are interrupted by noncoding sections of DNA known as introns that is shown in the figure. Nevertheless the triplet codons within the exons and the order of exons themselves in the gene

Figure: Structure and expression of a protein coding gene in a eukaryote.

is since colinear  with the amino acid sequence  of the determined  polypeptide.  Number of introns in the protein-coding gene differ and they range in size from about 80 bp to over 10 000 bp. The mainly transcript is a pre-mRNA molecule that must be processed to yield mature mRNA ready for translation.  In During RNA processing, the pre-mRNA receives a 5 cap and (commonly but not always) a poly (A) tail of about 200 A residues, and the intron sequences are erased through RNA splicing.