# How to Make Many Copies of a Specific DNA Segment > This patent describes the fundamental three-step process for making millions of copies of a specific piece of DNA using short starter molecules and an enzyme, a technique known as Polymerase Chain Reaction (PCR). - **Patent:** US 4683202 - **Original title:** Process for amplifying nucleic acid sequences - **Owner:** Cetus Corp - **Granted:** 1987 - **Status:** Public domain (expired) - **Times cited:** 7,558 - **Field:** biotech, pharmaceutical, diagnostics, gene_editing, research_tools, forensic_science ## What it does This patent details a process to amplify, or make many copies of, a specific nucleic acid sequence. First, two short DNA pieces called "oligonucleotide primers" attach to opposite ends of the target DNA (Claim 1a). An enzyme then builds new DNA strands starting from these primers, creating "extension products." Next, these newly made DNA strands are separated from their original templates, often by heating (Claim 1b, 3, 4). Finally, the separated single strands are again treated with the same primers and enzyme to build more new strands (Claim 1c). This cycle of separating and rebuilding is repeated multiple times (Claim 2), creating an exponentially increasing number of copies of the target DNA. For example, if you wanted to copy a specific gene from a human DNA sample, you would design primers that match the beginning and end of that gene, then run these cycles to produce millions of copies. ## What it does NOT cover - Does not cover methods that amplify DNA without using two distinct oligonucleotide primers for each strand of the target sequence. - Does not cover amplification processes that do not involve separating the primer extension products from their templates. - Does not cover methods where the extension product synthesized from one primer cannot serve as a template for the synthesis of the other primer's extension product. - Does not cover amplification techniques that do not repeat the separation and extension steps at least once. - Does not cover direct amplification of RNA without an initial reverse transcription step to convert it to DNA, even though reverse transcriptase is mentioned as an enzyme option for RNA templates (Claim 7). ## The clever bit The novelty lies in the cyclical nature of the process: using two primers that define the boundaries of a target sequence, repeatedly separating DNA strands, and then synthesizing new strands from those separated templates. This clever repetition leads to an exponential increase in the target DNA, making it detectable and usable from minute starting amounts. ## Real-world examples 1. COVID-19 diagnostic tests 2. Forensic DNA fingerprinting 3. Paternity testing 4. Genetic disease screening 5. Gene cloning 6. Archaeological DNA analysis ## Why it matters This patent covers the foundational method for Polymerase Chain Reaction (PCR), a technique that revolutionized molecular biology and biotechnology. PCR allows scientists to quickly make millions of copies of a specific DNA segment from a tiny sample. This capability is essential for genetic research, disease diagnosis, forensic science, and countless other applications, making it one of the most impactful scientific inventions of the 20th century. ## Frequently asked questions ### What does How to Make Many Copies of a Specific DNA Segment cover? This patent describes the fundamental three-step process for making millions of copies of a specific piece of DNA using short starter molecules and an enzyme, a technique known as Polymerase Chain Reaction (PCR). ### Who owns patent US 4683202? Cetus Corp owns this patent, granted in 1987. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 4683202 cited by? This patent has been cited by 7558 later patents that build on its ideas. ### What problem does this patent solve? This patent covers the foundational method for Polymerase Chain Reaction (PCR), a technique that revolutionized molecular biology and biotechnology. PCR allows scientists to quickly make millions of copies of a specific DNA segment from a tiny sample. This capability is essential for genetic research, disease diagnosis, forensic science, and countless other applications, making it one of the most impactful scientific inventions of the 20th century. ### What does this patent NOT cover? Does not cover methods that amplify DNA without using two distinct oligonucleotide primers for each strand of the target sequence. **Full plain-English explainer:** https://patentbrief.org/patent/us/4683202/pcr-polymerase-chain-reaction-mullis **Original patent:** https://patents.google.com/patent/US4683202 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How to Make Billions of Copies of a DNA Segment](https://patentbrief.org/patent/us/4683195/pcr-polymerase-chain-reaction) — This patent describes the Polymerase Chain Reaction (PCR), a method to rapidly create many copies of a specific piece of DNA or RNA, enabling its detection and analysis. - [How Scientists First Made DNA Replicate in New Cells](https://patentbrief.org/patent/us/4237224/cohen-boyer-recombinant-dna) — This 1980 patent describes a method for cutting and pasting DNA pieces in a lab to create new, self-replicating genetic material that can be inserted into bacteria, a foundational technique for genetic engineering. - [How to Sequence DNA from Tiny Samples Using Specialized Plates](https://patentbrief.org/patent/us/10456769/method-of-constructing-sequencing-library) — A method for preparing DNA for genetic sequencing by splitting tiny samples into a 5184-well plate to ensure accurate data from very few cells. - [How CRISPR-Cas9 Uses RNA to Edit DNA](https://patentbrief.org/patent/us/10113167/methods-and-compositions-for-rna-directed-target-dna-modification-and-for-rna-directed-modulation-of-transcription) — This patent describes the fundamental mechanism of using a two-part RNA system to guide the Cas9 protein to specific locations in DNA for precise editing. - [How to Edit Genes in Human Cells Using an Engineered CRISPR System](https://patentbrief.org/patent/us/8697359/crispr-gene-editing) — This patent describes an engineered CRISPR-Cas9 system for precisely cutting DNA in eukaryotic cells to change how genes work, opening the door for gene editing in complex organisms.