Liquid purification or separation – With means to add treating material – Chromatography
Reexamination Certificate
2001-07-24
2002-07-16
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
With means to add treating material
Chromatography
C210S635000, C210S656000, C422S070000
Reexamination Certificate
active
06419824
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus and method for separating, isolating, and purifying polynucleotides. In particular, this invention relates to methods and devices for separating targeted polynucleotide fragments having a predetermined base-pair length or range of base pair lengths, and for separating and purifying polynucleotides with both high pressure and low pressure devices.
BACKGROUND OF THE INVENTION
A need exists for rapid and efficient procedures for isolating, separating and purifying single-stranded oligonucleotides and single-stranded DNA fragments, RNA single-stranded DNA fragments, plasmids and the like. Traditional methods such as ion exchange chromatography, high pressure reverse phase chromatography, gel electrophoresis, capillary electrophoresis and the like are slow, laborious and inefficient, and they require the services of a highly skilled chromatographic expert. Furthermore, many methods are incapable of effecting a base-pair length size based separation of these fragments and are capable of yielding only minute quantities of separated materials.
Mixtures of single-stranded nucleic acid fragments having different base pair lengths are separated for numerous and diverse reasons. The ability to detect mutations in single-stranded polynucleotides, and especially in DNA fragments which have been amplified by PCR, presents a somewhat different problem since DNA fragments containing mutations are generally the same length as their corresponding wild type (defined herein below) but differ in base sequence.
DNA separation and mutation detection are of great importance in medicine, as well as in the physical and social sciences, as well as in forensic investigations. The Human Genome Project is providing an enormous amount of genetic information which is setting new criteria for evaluating the links between mutations and human disorders (Guyer, et al.,
Proc. Natl. Acad. Sci. USA
92:10841 (1995)). The ultimate source of disease, for example, is described by genetic code that differs from wild type (Cotton,
TIG
13:43 (1997)). Understanding the genetic basis of disease can be the starting point for a cure. Similarly, determination of differences in genetic code can provide powerful and perhaps definitive insights into the study of evolution and populations (Cooper, et. al.,
Human Genetics
69:201 (1985)). Understanding these and other issues related to genetic coding is based on the ability to identify anomalies, i.e., mutations, in a DNA fragment relative to the wild type. A need exists, therefore, for a methodology which can separate DNA fragments based on size differences as well as separate DNA having the same length but differing in base pair sequence (mutations from wild type), in an accurate, reproducible, reliable manner. Ideally, such a method would be efficient and could be adapted to routine high throughput sample screening applications.
DNA molecules are polymers comprising sub-units called deoxynucleotides. The four deoxynucleotides found in DNA comprise a common cyclic sugar, deoxyribose, which is covalently bonded to any of the four bases, adenine (a purine), guanine (a purine), cytosine (a pyrimidine), and thymine (a pyrimidine), hereinbelow referred to as A, G, C, and T respectively. A phosphate group links a 3′-hydroxyl of one deoxynucleotide with the 5′-hydroxyl of another deoxynucleotide to form a polymeric chain. In single-stranded DNA, two strands are held together in a helical structure by hydrogen bonds between, what are called, complimentary bases. The complimentarity of bases is determined by their chemical structures. In single-stranded DNA, each A pairs with a T and each G pairs with a C, i.e., a purine pairs with a pyrimidine. Ideally, DNA is replicated in exact copies by DNA polymerases during cell division in the human body or in other living organisms. DNA strands can also be replicated in vitro by means of the Polymerase Chain Reaction (PCR).
Sometimes, exact replication fails and an incorrect base pairing occurs, which after further replication of the new strand, results in single-stranded DNA offspring containing a heritable difference in the base sequence from that of the parent. Such heritable changes in base pair sequence are called mutations.
In the present invention, single-stranded DNA is referred to as a duplex. When a base sequence of one strand is entirely complimentary to a base sequence of the other strand, the duplex is called a homoduplex. When a duplex contains at least one base pair which is not complimentary, the duplex is called a heteroduplex. A heteroduplex is formed during DNA replication when an error is made by a DNA polymerase enzyme and a non-complimentary base is added to a polynucleotide chain being replicated. Further replications of a heteroduplex will, ideally, produce homoduplexes which are heterozygous, i.e., these homoduplexes will have an altered sequence compared to the original parent DNA strand. When the parent DNA has a sequence which predominates in a naturally occurring population, it is generally called “wild type”.
Many different types of DNA mutations are known. Examples of DNA mutations include, but are not limited to, “point mutation” or “single base pair mutations” wherein an incorrect base pairing occurs. The most common point mutations comprise “transitions” wherein one purine or pyrimidine base is replaced for another and “transversions” wherein a purine is substituted for a pyrimidine (and visa versa). Point mutations also comprise mutations wherein a base is added or deleted from a DNA chain. Such “insertions” or “deletions” are also known as “frameshift mutations”. Although they occur with less frequency than point mutations, larger mutations affecting multiple base pairs can also occur and may be important. A more detailed discussion of mutations can be found in U.S. Pat. No. 5,459,039 to Modrich (1995), and U.S. Pat. No. 5,698,400 to Cotton (1997). These references and the references contained therein are incorporated in their entireties herein.
The sequence of base pairs in DNA code for the production of proteins. In particular, a DNA sequence in the exon portion of a DNA chain codes for the corresponding amino acid sequence in a protein. Therefore, a mutation in a DNA sequence may result in an alteration in the amino acid sequence of a protein. Such an alteration in the amino acid sequence may be completely benign or may inactivate a protein or alter its function to be life threatening or fatal. On the other hand, mutations in an intron portion of a DNA chain would not be expected to have a biological effect since an intron section does not contain code for protein production. Nevertheless, mutation detection in an intron section may be important, for example, in a forensic investigation.
Detection of mutations is, therefore, of great interest and importance in diagnosing diseases, understanding the origins of disease and the development of potential treatments. Detection of mutations and identification of similarities or differences in DNA samples is also of critical importance in increasing the world food supply by developing diseases resistant and/or higher yielding crop strains, in forensic science, in the study of evolution and populations, and in scientific research in general (Guyer, et al.,
Proc. Natl. Acad. Sci. USA
92:10841 (1995); Cotton,
TIG
13:43 (1997)).
Alterations in a DNA sequence which are benign or have no negative consequences are sometimes called “polymorphisms”. In the present invention, any alterations in the DNA sequence, whether they have negative consequences or not, are denoted as “mutations”. It is to be understood that the method and system of this invention have the capability to detect mutations regardless of biological effect or lack thereof. For the sake of simplicity, the term “mutation” will be used throughout to mean an alteration in the base sequence of a DNA strand compared to a reference strand (generally, but not necessarily, wild type). It is to be understood that in the context of this i
Gjerde Douglas T.
Haefele Robert M.
Hanna Christopher P.
Legendre, Jr. Benjamin L.
Taylor Paul D.
Therkorn Ernest G.
Transgenomic Inc.
Walker William B.
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