How to Make Billions of Copies of a DNA Segment
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.
Original patent title: “Process for amplifying, detecting, and/or-cloning nucleic acid sequences”
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. Granted to Cetus Corp in 1987 with 30 claims and 6,231 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
This patent details a process for amplifying and detecting specific nucleic acid sequences. First, a sample containing DNA or RNA is treated with two short DNA pieces called oligonucleotide primers, one for each strand of the target sequence (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1a). These primers attach to the target, and an enzyme then extends them, building new complementary strands. Next, the sample is heated to separate the newly made strands from their original templates (denaturing, Claim 1b). The process of adding primers and extending them is then repeated, using the newly separated strands as templates (Claim 1c). Repeating these steps many times creates a massive number of copies of the target sequence (Claim 2). Finally, a labeled probe is added to detect if the amplified sequence is present (Claim 1d, 1e). For example, this process can detect a specific genetic mutation like the one causing sickle cell anemia (Claim 11, 12).
The gap
What does this patent NOT cover?
- Does not cover amplification methods that do not use two oligonucleotide primers for each strand of the target sequence.
- Does not cover detection methods that do not involve adding a labeled oligonucleotide probe after amplification.
- Does not cover processes where the primer extension products are not separated from their templates before further amplification steps.
- Does not cover amplification using enzymes that are inactivated by the high temperatures required for strand separation, unless a heat-stable enzyme is explicitly used (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 15).
- Does not cover methods that amplify nucleic acids without repeating the primer extension and denaturation steps at least once.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The core innovation was the realization that by repeatedly heating DNA to separate its strands and then cooling it to allow primers and an enzyme to build new copies, a specific DNA segment could be exponentially amplified. This cycling process, especially with a heat-stable enzyme (hinted at in ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 15), made PCR incredibly efficient and practical.
The Patent Drawing
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 (RT-PCR)
Forensic DNA analysis (e.g., crime scene investigation)
Paternity testing
Genetic disease screening (e.g., cystic fibrosis, sickle cell anemia)
Gene cloning and sequencing in research labs
Detection of pathogenic organisms in clinical samples
Why it matters
The bigger picture
This patent describes the Polymerase Chain Reaction (PCR), a foundational technique in molecular biology. It revolutionized genetic research, medical diagnostics, and forensic science by making it possible to study tiny amounts of DNA. The inventorinventorThe person who actually conceived the invention. Listed on the patent regardless of who owns it.Read more →, Kary Mullis, received the Nobel Prize in Chemistry for his work on PCR, highlighting its immense scientific impact. Cetus Corp, the original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, commercialized this technology, which became essential for countless applications.
Filed
February 7, 1986
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. These companies continuously innovate on PCR technology, creating faster, more sensitive, and more specialized versions. Diagnostic companies worldwide rely on PCR for their testing services.
Market impact
The introduction of PCR created an entirely new market for molecular diagnostic tools and research reagents. It enabled the rapid and accurate detection of diseases, transformed forensic science, and became indispensable for genetic engineering and basic biological research. The technology's broad utility led to widespread adoption, making it a cornerstone of modern biotechnology and medicine.
Claim 1 — Plain English
What this patent covers
This patent details a process for amplifying and detecting specific nucleic acid sequences. First, a sample containing DNA or RNA is treated with two short DNA pieces called oligonucleotide primers, one for each strand of the target sequence (Claim 1a). These primers attach to the target, and an enzyme then extends them, building new complementary strands. Next, the sample is heated to separate the newly made strands from their original templates (denaturing, Claim 1b). The process of adding primers and extending them is then repeated, using the newly separated strands as templates (Claim 1c). Repeating these steps many times creates a massive number of copies of the target sequence (Claim 2). Finally, a labeled probe is added to detect if the amplified sequence is present (Claim 1d, 1e). For example, this process can detect a specific genetic mutation like the one causing sickle cell anemia (Claim 11, 12).
The clever bit
The core innovation was the realization that by repeatedly heating DNA to separate its strands and then cooling it to allow primers and an enzyme to build new copies, a specific DNA segment could be exponentially amplified. This cycling process, especially with a heat-stable enzyme (hinted at in Claim 15), made PCR incredibly efficient and practical.
What it does not cover
- Does not cover amplification methods that do not use two oligonucleotide primers for each strand of the target sequence.
- Does not cover detection methods that do not involve adding a labeled oligonucleotide probe after amplification.
- Does not cover processes where the primer extension products are not separated from their templates before further amplification steps.
- Does not cover amplification using enzymes that are inactivated by the high temperatures required for strand separation, unless a heat-stable enzyme is explicitly used (Claim 15).
- Does not cover methods that amplify nucleic acids without repeating the primer extension and denaturation steps at least once.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Strong
Citation count
40/40
Highly cited
Claim breadth
20/20
Very broad protection
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
$146K – $468K
Midpoint $293K · expired or expiring · industry ×3.0
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
30 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Saiki, R. K., Scharf, S. J., Mullis, K. B., Arnheim, N., Erlich, H. A., & Horn, G. T. (1987). How to Make Billions of Copies of a DNA Segment (U.S. Patent No. 4,683,195). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4683195/pcr-polymerase-chain-reaction
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 Billions of Copies of a DNA Segment cover?
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.
Who owns patent US 4683195?
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 4683195 cited by?
This patent has been cited by 6231 later patents that build on its ideas.
What problem does this patent solve?
This patent describes the Polymerase Chain Reaction (PCR), a foundational technique in molecular biology. It revolutionized genetic research, medical diagnostics, and forensic science by making it possible to study tiny amounts of DNA. The inventor, Kary Mullis, received the Nobel Prize in Chemistry for his work on PCR, highlighting its immense scientific impact. Cetus Corp, the original assignee, commercialized this technology, which became essential for countless applications.
What does this patent NOT cover?
Does not cover amplification methods that do not use two oligonucleotide primers for each strand of the target sequence.
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