How are introns related to the RNA coding segment?

Introns are non-coding segments of a gene that are interspersed among the coding exons in the DNA sequence. During the process of transcribing DNA to RNA, both introns and exons are initially included in the primary RNA transcript (pre-mRNA). However, before the mature mRNA is formed and translated into protein, the introns must be removed through a process called RNA splicing.

This splicing ensures that only the coding regions (exons) remain in the final mRNA, which is then translated into proteins. Therefore, the correct answer highlights the crucial role of introns being removed during RNA processing, thereby enabling the synthesis of functional proteins from the processed mRNA.

The other options, while related to RNA and genes, do not accurately describe the nature of introns. For example, introns are not part of the RNA sequence in the final mature mRNA since they are excised out. They do not inherently increase the length of the mRNA in terms of coding function since only the exons contribute to the final protein. Additionally, introns are not translated into proteins; they are non-coding regions that play regulatory or structural roles rather than coding for amino acids.