National Academies Press: OpenBook

DNA Technology in Forensic Science (1992)

Chapter:GLOSSARY

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Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
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Glossary


A

single-letter designation of the purine base adenine; also used in diagrams to represent a nucleotide containing adenine

Adenine

a purine base; one of the four nitrogen-containing molecules present in nucleic acids DNA and RNA; designated by the letter A

Allele

one of two or more alternative forms of a gene

Allele frequency

the proportion of a particular allele among the chromosomes carried by individuals in a population

AMP-FLP

amplified fragment length polymorphism

Autoradiogram (autoradiograph; autorad)

a photographic recording of the positions on a film where radioactive decay of isotopes has occurred

AutosomeY

any of the chromosomes other than the sex chromosomes, X and


Band

the visual image representing a particular DNA fragment on an autoradiogram

Band shift

the phenomenon in which DNA fragments in one lane of a gel migrate at a rate different from that of identical fragments in other lanes of the same gel

Basepair

two complementary nucleotides held together by hydrogen bonds; basepairing occurs between A and T and between G and C

Biallelic

(see Diallelic)

Blot

see Southern blot

Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
×

C

single-letter designation of the pyrimidine base cytosine; also used in diagrams to represent a nucleotide containing cytosine

Chromosome

the structure by which hereditary information is physically transmitted from one generation to the next; the organelle that carries the genes

Controls

tests performed in parallel with experimental samples and designed to demonstrate that a procedure worked correctly

Cytosine

a pyrimidine base; one of the four nitrogen-containing molecules in nucleic acids DNA and RNA; designated by the letter C


Degradation

the breaking down of DNA by chemical or physical means

Denaturation

the process of unfolding of the complementary double strands of DNA to form single strands

Deoxyribonucleic acid (DNA)

the genetic material of organisms, usually double-stranded—composed of two complementary chains of nucleotides in the form of a double helix; a class of nucleic acids characterized by the presence of the sugar deoxyribose and the four bases adenine, cytosine, guanine, and thymine

Diallelic DNA

variation showing only two forms with a frequency of more than 1%

Diploid

having two sets of chromosomes, in pairs (compare haploid)

DNA

deoxyribonucleic acid

DNA band

the visual image representing a particular DNA fragment on an autoradiogram

DNA databank (database)

a collection of DNA typing profiles of selected or randomly chosen individuals

DNA polymerase

an enzyme that catalyzes the synthesis of double-stranded DNA

DNA probe

a short segment of single-stranded DNA labeled with a radioactive or chemical tag that is used to detect the presence of a particular DNA sequence through hybridization to its complementary sequence


Electrophoresis

a technique in which different molecules are separated by their rate of movement in an electric field

Enzyme

a protein that is capable of speeding up a specific chemical reaction but which itself is not changed or consumed in the process; a biological catalyst

Ethidium bromide

an organic molecule that binds to DNA and fluoresces under ultraviolet light and is used to identify DNA


G

single-letter designation of the purine base guanine; also used in diagrams to represent a nucleotide containing guanine

Gamete

a haploid reproductive cell

Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
×

Gametic (phase) equilibrium

the state at loci on different chromosomes when the allele at one locus in the gamete varies independently of that at the other loci; in gametic (phase) disequilibrium, a specific allele at one locus is associated with an allele at another locus on a different chromosome with a frequency greater than expected by chance (see linkage disequilibrium)

Gel

semisolid matrix (usually agarose or acrylamide) used in electrophoresis to separate molecules

Gene

the basic unit of heredity; a sequence of DNA nucleotides on a chromosome

Gene frequency

the relative occurrence of a particular allele in a population

Genetic drift

random fluctuation in allele frequencies

Genome

the total genetic makeup of an organism

Genotype

the genetic makeup of an organism, as distinguished from its physical appearance or phenotype

Guanine

a purine base; one of the four nitrogen-containing molecules present in nucleic acids DNA and RNA; designated by the letter G


Haploid

having one set of chromosomes (compare diploid)

Hardy-Weinberg

equilibrium the condition, for a particular genetic locus and a particular population, with the following properties: allele frequencies at the locus are constant in the population over time and there is no statistical correlation between the two alleles possessed by individuals in the population; such a condition is approached in large randomly mating populations in the absence of selection, migration, and mutation

Heredity

the transmission of characteristics from parent to offspring

Heterozygote

a diploid organism that carries different alleles at one or more genetic loci on its homologous chromosomes

Heterozygous

having different alleles at a particular locus; for most forensic DNA probes, the autoradiogram displays two bands if the person is heterozygous at the locus

HLA

see human leukocyte antigen

Homology

similarity between two structures or functions indicative of a common evolutionary origin

Homozygote

a diploid organism that carries identical alleles at one or more genetic loci on its homologous chromosomes

Homozygous

having the same allele at a particular locus; for most forensic DNA probes, the autoradiogram displays a single band if the person is homozygous at the locus

Human leukocyte antigen (HLA)

protein-sugar structures on the surface of most cells, except blood cells, that differ among individuals and are

Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
×

important for acceptance or rejection of tissue grafts or organ transplants; the locus of one particular class, HLA DQ, is used for forensic analysis with PCR

Hybridization

the reassociation of complementary strands of nucleic acids, nucleotides, or probes


Isotope

an alternative form of a chemical element; used particularly in reference to the radioactive alternative forms, or radioisotopes


Linkage

disequilibrium the phenomenon in which a specific allele at one locus is non-randomly associated with an allele at another locus

Locus (pl. loci)

the specific physical location of a gene on a chromosome


Marker

a gene with a known location on a chromosome and a clear-cut phenotype that is used as a point of reference in the mapping of other loci

Membrane

the matrix (usually nylon) to which DNA is transferred during the Southern blotting procedure

Molecular-weight size marker

DNA fragments of known size, from which the size of an unknown DNA sample can be determined

Monomorphic probe

a probe that detects the same allele and hence the same pattern in everyone

Multilocus probe

a DNA probe that detects genetic variation at multiple sites; an autoradiogram of a multilocus probe yields a complex, stripelike pattern of 30 or more bands per individual

Mutagen

a physical agent (e.g., x rays) or chemical agent that induces changes in DNA


Nucleic acid

a nucleotide polymer of which major types are DNA and RNA

Nucleotide

a unit of nucleic acid composed of phosphate, a five-carbon sugar (ribose or deoxyribose), and a purine or a pyrimidine base


PCR

polymerase chain reaction

Phenotype

the physical appearance or functional expression of a trait

Point mutation

an alteration of one nucleotide in chromosomal DNA that consists of addition, deletion, or substitution of nucleotides

Polymerase chain reaction (PCR)

an in vitro process that yields millions of copies of desired DNA through repeated cycling of a reaction that involves the enzyme DNA polymerase

Polymorphism

the presence of more than one allele of a gene in a population at a frequency greater than that of a newly arising mutation; opera-

Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
×

tionally, a population in which the most common allele at a locus has a frequency of less than 99%

Population

a group of individuals occupying a given area at a given time

Probe

a short segment of single-stranded DNA tagged with a reporter molecule, such as radioactive phosphorus atom, that is used to detect a particular complementary DNA sequence

Proficiency tests

tests to evaluate the competence of technicians and the quality performance of a laboratory; in open tests, the technicians are aware that they are being tested, but in blind tests, they are not aware; internal proficiency tests are conducted by the laboratory itself, and external tests are conducted by an agency independent of the laboratory being tested

Protein

a chain of amino acids joined by peptide bonds

Purine

the larger of two kinds of bases found in DNA and RNA; a nitrogenous base with a double-ring structure, such as adenine or guanine (compare pyrimidine)

Pyrimidine

the smaller of two kinds of bases found in DNA and RNA; a nitrogenous base with a single-ring structure, such as cytosine, thymine, and uracil (compare purine)


Quality assurance

a program conducted by a laboratory to ensure accuracy and reliability of tests performed

Quality control

internal activities or activities according to externally established standards used to monitor the quality of DNA typing to meet and satisfy specified criteria


Recombinant DNA

fragments of DNA from two different species, such as a bacterium and a mammal, spliced into a single molecule

Replication

the synthesis of new DNA from existing DNA

Restriction endonuclease, restriction enzyme

an enzyme that cleaves DNA molecules at particular base sequences

Restriction fragment length polymorphism (RFLP)

variation in the length of DNA fragments produced by a restriction endonuclease that cuts at a polymorphic locus

RFLP

restriction fragment length polymorphism

RFLP analysis

technique that uses single-locus or multi-locus probes to detect variation in a DNA sequence according to differences in the length of fragments created by cutting DNA with a restriction enzyme

Ribonucleic acid (RNA)

a class of nucleic acids characterized by the presence of the sugar ribose and the pyrimidine uracil, as opposed to the thymine of DNA

RNA

ribonucleic acid

Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
×

Serology

the discipline concerned with the immunologic study of body fluids

Serum

the liquid that separates from blood after coagulation

Sex chromosomes (x and y chromosomes)

chromosomes that are different in the two sexes and that are involved in sex determination

Sex-linked characteristic

a genetic characteristic, such as color blindness, that is determined by a gene on a sex chromosome and shows a different pattern of inheritance in males and females; X-linked is a more specific term

Single-locus probe

a DNA probe that detects genetic variation at only one site in the genome; an autoradiogram that uses one single-locus probe usually displays one band in homozygotes and two bands in heterozygotes

Somatic cells

the differentiated cells that make up the body tissues of multicellular plants and animals

Southern blot

the nylon membrane to which DNA adheres after the process of Southern blotting

Southern blotting

the technique for transferring DNA fragments that have been separated by electrophoresis from the gel to a nylon membrane

Standards

criteria established for quality control and quality assurance; established or known test reagents, such as molecular-weight standards


T

single-letter designation of the pyrimidine base thymine; also used in diagrams to represent a nucleotide containing thymine

Tandem repeats

multiple copies of an identical DNA sequence arranged in direct succession in a particular region of a chromosome

Taq polymerase

a DNA polymerase used to form double-stranded DNA from nucleotides and a single-stranded DNA template in the PCR technique

Thymine

a pyrimidine base; one of the four nitrogen-containing molecules present in nucleic acids DNA and RNA; designated by the letter T


Uracil

a pyrimidine in RNA


Variable number of tandem repeats (VNTR)

repeating units of a DNA sequence for which the number varies between individuals

VNTR

variable number of tandem repeats


Zygote

diploid cell that results from the fusion of male and female gametes

Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
×
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Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
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Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
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Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
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Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
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Suggested Citation:"GLOSSARY." National Research Council. 1992. DNA Technology in Forensic Science. Washington, DC: The National Academies Press. doi: 10.17226/1866.
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Matching DNA samples from crime scenes and suspects is rapidly becoming a key source of evidence for use in our justice system. DNA Technology in Forensic Science offers recommendations for resolving crucial questions that are emerging as DNA typing becomes more widespread.

The volume addresses key issues:

  • Quality and reliability in DNA typing, including the introduction of new technologies, problems of standardization, and approaches to certification.
  • DNA typing in the courtroom, including issues of population genetics, levels of understanding among judges and juries, and admissibility.
  • Societal issues, such as privacy of DNA data, storage of samples and data, and the rights of defendants to quality testing technology.

Combining this original volume with the new update—The Evaluation of Forensic DNA Evidence—provides the complete, up-to-date picture of this highly important and visible topic.

This volume offers important guidance to anyone working with this emerging law enforcement tool: policymakers, specialists in criminal law, forensic scientists, geneticists, researchers, faculty, and students.

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