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).
Original patent title: “Process for amplifying nucleic acid sequences”
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). Granted to Cetus Corp in 1987 with 23 claims and 7,558 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
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 (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 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.
The gap
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.
- 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 (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 7).
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The noveltynoveltyThe requirement that an invention be different from anything publicly known before its priority date.Read more → 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.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
COVID-19 diagnostic tests
Forensic DNA fingerprinting
Paternity testing
Genetic disease screening
Gene cloning
Archaeological DNA analysis
Why it matters
The bigger picture
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.
Filed
October 25, 1985
Granted
July 28, 1987
Market context
Who's building on this
Companies in this space
Companies like Thermo Fisher Scientific, Bio-Rad Laboratories, and Qiagen are major players in developing and selling PCR instruments, reagents, and kits. Academic and industrial research labs globally rely on PCR for a vast array of applications, from basic science to drug discovery and development. The original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, Cetus Corp, was acquired, but its legacy through this invention continues to underpin much of modern molecular biology.
Market impact
This patent laid the groundwork for the entire PCR market, which grew into a multi-billion dollar industry. It enabled rapid and sensitive detection of specific DNA sequences, transforming fields like medical diagnostics, genetic research, and forensics. The subsequent development and patenting of thermostable DNA polymerases (like Taq polymerase, though not explicitly named in this patent's claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →) further streamlined the process, making it automated and widely accessible, leading to its ubiquitous adoption across scientific disciplines.
Claim 1 — Plain English
What this patent covers
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.
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.
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).
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
15/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$59K – $187K
Midpoint $117K · expired or expiring · industry baseline
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
23 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Mullis, K. B. (1987). How to Make Many Copies of a Specific DNA Segment (U.S. Patent No. 4,683,202). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4683202/pcr-polymerase-chain-reaction-mullis
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
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.
Same assignee
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