Cistron

A cistron is a functional unit of genetic information that can be expressed as a single RNA transcript. It is the basic unit of transcription and is defined by the sequence of nucleotides in a gene. The term "cistron" was coined by Francis Crick in 1958 to distinguish it from the "gene," which was previously used to describe the functional unit of heredity. A cistron can be further divided into exons, which are the segments of the DNA that are transcribed into RNA, and introns, which are the non-coding segments that are removed during RNA processing.

Cistrons are essential for the expression of genetic information, as they contain the instructions for the synthesis of proteins. The process of transcription, where a DNA sequence is copied into an RNA molecule, occurs at the level of the cistron. This RNA molecule can then be translated into a protein through the process of translation.

In some cases, a single gene may contain multiple cistrons, each capable of producing a different RNA transcript. This is known as polycistronic transcription, where multiple cistrons are transcribed into a single RNA molecule. Alternatively, a single cistron may produce multiple RNA transcripts through alternative splicing, where different combinations of exons are used to create different RNA molecules.

The concept of the cistron is fundamental to understanding the molecular basis of inheritance and the regulation of gene expression. It provides a framework for studying how genetic information is transcribed and translated into functional proteins, which are crucial for the structure and function of living organisms.