Q. 4. Define a cistron. Giving examples differentiate between monocistronic and polycistronic unit.
A cistron is a stretch of base sequences that codes for one polypeptide chain including adjacent control regions. It may also code fr a tRNA molecule or may perform other specific functions including regulating functions of other cistrons.
This term has replaced the definition of a gene. Monocistronic transcription unit will have all the regulatory and coding sequences for a single polypeptide, whereas polycistronic may have coding sequences for more than one polypeptide.
In eukaryotic cells almost all the messenger RNAs are monocistronic. In prokaryotes, lac operon coding sequence would be an example of a polycistronic DNA region.
© 2024 GoodEd Technologies Pvt. Ltd.
