You can freely build on How Scientists First Made DNA Replicate in New Cells

What this patent covers

This patent details a process for creating 'biologically functional DNA' outside of a living cell, then introducing it into a microorganism, like bacteria, so it can make copies of itself and potentially produce specific proteins. The method involves cutting a circular DNA molecule (like a plasmid or virus DNA) into a linear piece with specific ends, then attaching another piece of DNA that contains a desired gene. This combined DNA, called a 'replicon,' is designed to be able to replicate within a host cell. The patent specifically mentions creating 'transformants' – cells that have successfully incorporated this new DNA. A key part is using a gene for a 'phenotypical trait,' like resistance to a substance, to easily identify the modified cells from the original ones. For example, claim 4 describes using resistance to a growth-inhibiting substance to select for bacteria that have taken up the new DNA.

What is now free to use

All 1 claims of US 4237224 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover methods where the DNA is not prepared 'in vitro' (in a lab).

• Does not cover DNA segments that do not contain an intact 'replicon' (the part needed for self-replication).

• Does not cover inserting DNA into organisms other than unicellular ones like bacteria.

• Does not cover the use of DNA segments that cannot be 'ligated' or joined together by their ends.

• Does not cover the production of proteins in organisms that naturally exchange genetic information with the source of the gene.

Who is building on this today

The foundational principles described here are universally applied across the biotechnology and pharmaceutical industries. Major companies like Genentech (a pioneer in the field), Amgen, and Pfizer, as well as countless academic labs and smaller biotech startups, rely on these core recombinant DNA techniques for drug development and biological research.

Products built on expired version of this technology

How to cite this patent in your documentation

Leland Stanford Junior University. US Patent 4237224. Process for producing biologically functional molecular chimeras. Granted 1980, expired 1999. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.