# How to Measure Gene Activity Using Competitive PCR Kits

> A laboratory method and kit for accurately measuring how much a specific gene is being used by cells by comparing it against a known internal standard.

- **Patent:** US 5639606
- **Original title:** Method for quantitative measurement of gene expression using multiplex competitive reverse transcriptase-polymerase chain reaction
- **Owner:** University of Rochester
- **Granted:** 1997
- **Status:** Public domain (expired)
- **Times cited:** 151
- **Field:** biotech

## What it does

This patent describes a kit used to quantify gene expression in small biological samples. It works by performing a multiplex reaction, meaning it amplifies both a target gene and a 'housekeeping' gene (a gene that is always active) at the same time. The kit includes competitive templates for both genes, which are nearly identical to the natural genes but contain a small point mutation. By adding these templates, researchers can compare the amount of product from the natural gene against the known amount of the competitive template, allowing for a precise calculation of how much of the target gene was originally present.

## What it does NOT cover

- Does not cover non-competitive PCR methods where no internal standard template is used.
- Does not cover gene expression measurement techniques that rely on sequencing or hybridization arrays.
- Does not cover the use of competitive templates that differ from the target by more than a point mutation.
- Does not cover methods that amplify the target and housekeeping genes in separate, non-multiplexed reactions.

## The clever bit

By using a competitive template that is nearly identical to the target gene, the method ensures that both the target and the competitor compete equally for the same primers and enzymes, effectively canceling out variations in reaction efficiency.

## Real-world examples

1. Oncology research for measuring tumor gene expression
2. Molecular diagnostic assays
3. Gene expression profiling in clinical biopsies

## Why it matters

Before this method, quantifying gene expression in tiny tissue samples was notoriously difficult and prone to error. This approach provided a standardized way to normalize data using housekeeping genes, which became a staple technique in molecular biology research for studying diseases like cancer.

## Frequently asked questions

### What does How to Measure Gene Activity Using Competitive PCR Kits cover?

A laboratory method and kit for accurately measuring how much a specific gene is being used by cells by comparing it against a known internal standard.

### Who owns patent US 5639606?

University of Rochester owns this patent, granted in 1997.

### 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 5639606 cited by?

This patent has been cited by 151 later patents that build on its ideas.

### What problem does this patent solve?

Before this method, quantifying gene expression in tiny tissue samples was notoriously difficult and prone to error. This approach provided a standardized way to normalize data using housekeeping genes, which became a staple technique in molecular biology research for studying diseases like cancer.

### What does this patent NOT cover?

Does not cover non-competitive PCR methods where no internal standard template is used.

**Full plain-English explainer:** https://patentbrief.org/patent/us/5639606/quantitative-pcr

**Original patent:** https://patents.google.com/patent/US5639606

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._