OCR GCSE Biology Practice Exam 2026 – Comprehensive All-in-One Guide to Exam Success

Plasmids are small, circular pieces of DNA that are found in the cytoplasm of bacterial cells as well as in some eukaryotic cells. They are distinct from the chromosomal DNA, which is often linear or larger in size. The circular structure of plasmids allows them to replicate independently of the chromosomal DNA, making them useful for various functions, such as carrying genes that provide antibiotic resistance or other advantageous traits. This unique structure is crucial for their role in genetic engineering and molecular cloning, where plasmids are often utilized as vectors to introduce new genes into organisms.