Question

What is cistron?

Answer 1

Hint: Cistron is the part of genetic material that helps in the coding of various proteins. It carries genetic information and plays an important role during the process of synthesis of chain or protein molecules.

Complete answer:
Cistron is also known as a gene. They carry genetic material and show their property during the cis-trans test. When the two alleles of genes are found, then the traits or changes that occur in both the alleles will be a dominant trait as in both the cistron complement mutation is taking place while on the other hand when in the two cistron complements only one complement shows changes while other remains same then it shows recessive mutation. For example, the operon model consists of various cistrons thus called polycistronic while the simple genes are said to be monocistronic as it contains only one cistron.
A Transcription unit that comprises the various nucleotide sequences present in the DNA strand which are helpful in the coding and formation of RNA. In the case of eukaryotes, it is monocistronic while in the case of prokaryotes it is polycistronic. The transcription unit consists of a promoter region, structural gene, and a termination region. In between the monocistronic structural gene interrupting coding sequences are found in the case of the eukaryotes. Exons are the coding sequence that is found in the mature RNA or mRNA while introns (intervening sequences) are absent. The process of removal of introns is known as ‘splicing’.
Genes are of two types: monocistronic or polycistronic.
-When only one gene is expressed through a promoter region then it is called Monocistronic mRNA. Each of them has its own promoter and terminator region.
-When several proteins are expressed then it is called Polycistronic mRNA that is generally found in various bacterial and chloroplast mRNAs. Polycistronic mRNAs consist of a leader sequence that precedes the first gene. Here many genes are present per promoter region.

Note:
The terms cistron and gene are synonyms or alternatives to each other. Seymour Benzer was the first to coin the word Cistron. He called cistrons ‘the elementary units of heredity’. They are usually used in the cis-trans test also called the complementation test.