Glossary / Science

Genetics Glossary

3-End: The end of a polynucleotide with a free (or phosphorylated) 3' - hydroxyl group.
5-End: The end of a polynucleotide with a free (or phosphorylated or capped) 5' - hydroxyl group: transcrip
Achondroplasia: The most common and well known form of short limbed dwarfism characterized by a normal trunk size wi
Additive Genetic Effects: When the combined effects of alleles at different loci are equal to the sum of their individual effe
Adenine (A): A nitrogenous base, one member of the base pair a- t (adenine- thymine).
Advanced Maternal Age: Women over age 34 (age 35 at delivery) at increased risk for nondisjunction trisomy in fetus.
Affected Relative Pair: Individuals related by blood, each of whom is affected with the same trait. Examples are affected si
Aggregation Technique: A technique used in model organism studies in which embryos at the 8-cell stage of development are p
Alcoholism: A chronic and progressive condition characterized by the inability to control the consumption of alc
Allele: Alternative form of a genetic locus: a single allele for each locus is inherited from each parent (e
Allogeneic: Variation in alleles among members of the same species.
Alpha-Fetoprotein (AFP): A protein excreted by the fetus into the amniotic fluid and from there into the mother's bloodstream
Alternative Splicing: Different ways of combining a gene's exons to make variants of the complete protein
Alu Repetitive Sequence: The most common dispersed repeated dna sequence in the human genome accounting for 5% of human dna.
Amino Acid: Any of a class of 20 molecules that are combined to form proteins in living things. The sequence of
Amino Acid Sequence: The linear order of the amino acids in a protein or peptide.
Amniocentesis: Prenatal diagnosis method using cells in the amniotic fluid to determine the number and kind of chro
Amniocyte: Cells obtained by amniocentesis.
Amplification: An increase in the number of copies of a specific dna fragment: can be in vivo or in vitro.
Amplification: An increase in the number of copies of a specific dna fragment: can be in vivo or in vitro.
Aneuploidy: State of having variant chromosome number (too many or too few). (i.e. Down syndrome, turner syndrom
Angelman Syndrome: A condition characterized by severe mental deficiency, developmental delay and growth deficiency, pu
Anticipation: Each generation of offspring has increased severity of a genetic disorder: e.g., a grandchild may ha
Antisense: Nucleic acid that has a sequence exactly opposite to an mrna molecule made by the body: binds to the
Apert Syndrome: A condition caused by the premature closure of the sutures of the skull bones, resulting in an alter
Apoptosis: Programmed cell death, the body's normal method of disposing of damaged, unwanted, or unneeded cells
Arrayed Library: Individual primary recombinant clones (hosted in phage, cosmid, yac, or other vector) that are place
Artificial Insemination: The placement of sperm into a female reproductive tract or the mixing of male and female gametes by
Assembly: Putting sequenced fragments of dna into their correct chromosomal positions.
Autoradiography: A technique that uses x-ray film to visualize radioactively labeled molecules or fragments of molecu
Autosomal Dominant: A gene on one of the non-sex chromosomes that is always expressed, even if only one copy is present.
Autosome: A chromosome not involved in sex determination. The diploid human genome consists of 46 chromosomes,
Avuncular Relationship: The genetic relationship between nieces and nephews and their aunts and uncles.
Backcross: A cross between an animal that is heterozygous for alleles obtained from two parental strains and a
Bacterial Artificial Chromosome (BAC): A vector used to clone dna fragments (100- to 300-kb insert size: average, 150 kb) in escherichia co
Bacteriophage: A virus whose host is a bacterium: commonly called phage.
Barr Body: The condensed single x-chromosome seen in the nuclei of somatic cells of female mammals. Base pair a
Base: One of the molecules that form dna and rna molecules.
Base Pair (BP): Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two
Base Sequence: A partnership of organic bases found in dna and rna: adenine forms a base pair with thymine (or urac
Base Sequence Analysis: A method, sometimes automated, for determining the base sequence.
Baysian Analysis: A mathematical method to further refine recurrence risk taking into account other known factors.
Becker Muscular Dystrophy: X-linked condition characterized by progressive muscle weakness and wasting: manifests later in life
Behavioral Genetics: The study of genes that may influence behavior.
Bioinformatics: The science of managing and analyzing biological data using advanced computing techniques. Especiall
Bioremediation: The use of biological organisms such as plants or microbes to aid in removing hazardous substances f
Biotechnology: A set of biological techniques developed through basic research and now applied to research and prod
Birth Defect: Any harmful trait, physical or biochemical, present at birth, whether a result of a genetic mutation
Blast: A computer program that identifies homologous (similar) genes in different organisms, such as human,
Blast: A computer program that identifies homologous (similar) genes in different organisms, such as human,
Cancer: Diseases in which abnormal cells divide and grow unchecked. Cancer can spread from its original site
Candidate Gene: A gene located in a chromosome region suspected of being involved in a disease.
Capillary Array: Gel-filled silica capillaries used to separate fragments for dna sequencing. The small diameter of t
Carcinogen: Something which causes cancer to occur by causing changes in a cell's dna.
Carrier: An individual who possesses an unexpressed, recessive trait.
Cdna: Complementary dna produced from a rna template by the action of rna- dependent dna polymerase.
Cdna Library: A collection of dna sequences that code for genes. The sequences are generated in the laboratory fro
Cell: The basic unit of any living organism that carries on the biochemical processes of life.
Centimorgan (CM): A unit of measure of recombination frequency. One centimorgan is equal to a 1% chance that a marker
Centromere: A region of a chromosome to which spindle traction fibers attach during mitosis and meiosis: the pos
Charcot-Marie Tooth Disease: A condition characterized by degeneration of the motor and sensory nerves that control movement and
Chimera (Pl Chimaera): An organism that contains cells or tissues with a different genotype. These can be mutated cells of
Chimeraplasty: An experimental targeted repair process in which a desirable sequence of dna is combined with rna to
Chloroplast Chromosome: Circular dna found in the photosynthesizing organelle (chloroplast) of plants instead of the cell nu
Chorionic Villus Sampling: An invasive prenatal diagnostic procedure involving removal of villi from the human chorion to obtai
Chromomere: One of the serially aligned beads or granules of a eukaryotic chromosome, resulting from local coili
Chromosomal Deletion: The loss of part of a chromosome's dna.
Chromosomal Inversion: Chromosome segments that have been turned 180 degrees. The gene sequence for the segment is reversed
Chromosome: The self-replicating genetic structure of cells containing the cellular dna that bears in its nucleo
Chromosome Banding: A technique for staining chromosomes so that bands appear in a unique pattern particular to the chro
Chromosome Painting: Attachment of certain fluorescent dyes to targeted parts of the chromosome. Used as a diagnositic fo
Chromosome Region P: A designation for the short arm of a chromosome.
Chromosome Region Q: A designation for the long arm of a chromosome.
Chromosomes: The self- replicating genetic structures of cells containing the cellular dna that bears in its nucl
Cleft Palate: Congenital condition with cleft lip alone, or with cleft palate: cause is thought to be multifactori
Clone: An exact copy made of biological material such as a dna segment (e.g., a gene or other region), a wh
Cloned DNA: Any dna fragment that passively replicates in the host organism after it has been joined to a clonin
Clones: A group of cells derived from a single ancestor.
Cloning: Using specialized DNA technology to produce multiple, exact copies of a single gene or other segment
Cloning Vector: Dna molecule originating from a virus, a plasmid, or the cell of a higher organism into which anothe
Codominance: Situation in which two different alleles for a genetic trait are both expressed.
Codon: A sequence of three nucleotides in mrna that specifies an amino acid.
Coisogenic Or Congenic: Nearly identical strains of an organism: they vary at only a single locus.
Comparative Genomics: The study of human genetics by comparisons with model organisms such as mice, the fruit fly, and the
Complementary DNA (CDNA): Dna that is synthesized from a messenger rna template: the single-stranded form is often used as a p
Complementary Sequence: Nucleic acid base sequence that can form a double-stranded structure with another dna fragment by fo
Complex Trait: Trait that has a genetic component that does not follow strict mendelian inheritance. May involve th
Confidentiality: In genetics, the expectation that genetic material and the information gained from testing that mate
Congenital: Any trait present at birth, whether the result of a genetic or nongenetic factor.
Consanguinity: Genetic relationship. Consanguineous individuals have at least one common ancestor in the preceding
Conservative Change: An amino acid change that does not affect significantly the function of the protein.
Conserved Sequence: A base sequence in a dna molecule (or an amino acid sequence in a protein) that has remained essenti
Conserved Sequence: A base sequence in a dna molecule (or an amino acid sequence in a protein) that has remained essenti
Constitutive Ablation: Gene expression that results in cell death.
Contig: Group of cloned (copied) pieces of dna representing overlapping regions of a particular chromosome.
Contig Map: A map depicting the relative order of a linked library of overlapping clones representing a complete
Contigs: Groups of clones representing overlapping regions of a genome.
Contiguous Genes: Genes physically close on a chromosome that when acting together express a phenotype.
Cornelia De Lange Syndrome: Condition involving growth deficiency, significant developmental delay, anomalies of the extremities
Cosmid: Artificially constructed cloning vector containing the cos gene of phage lambda. Cosmids can be pack
Cpg Islands: Areas of multiple cg repeats in dna.
Cri-Du-Chat Syndrome: A chromosomal condition (monosomy 5p). Name comes from the distinctive mewing cry of affected infant
Crossing Over: The breaking during meiosis of one maternal and one paternal chromosome, the exchange of correspondi
Crossovers: The exchange of genetic material between two paired chromosome during meiosis.
Cystic Fibrosis: An autosomal recessive genetic condition of the exocrine glands, which causes the body to produce ex
Cytogenetics: The study of the physical appearance of chromosomes.
Cytological Band: An area of the chromosome that stains differently from areas around it.
Cytological Map: A type of chromosome map whereby genes are located on the basis of cytological findings obtained wit
Cytoplasmic Trait: A genetic characteristic in which the genes are found outside the nucleus, in chloroplasts or mitoch
Cytosine (C): A nitrogenous base, one member of the base pair gc (guanine and cytosine) in dna.
Data Warehouse: A collection of databases, data tables, and mechanisms to access the data on a single subject.
Degenerate Codon: A codon that specifies the same amino acid as another codon.
Deletion: The loss of a segment of the genetic material from a chromosome.
Deletion Map: A description of a specific chromosome that uses defined mutations --specific deleted areas in the g
Deletion Mapping: The use of overlapping deletions to localize the position of an unknown gene on a chromosome or link
Deoxyribonucleic Acid (DNA): The molecule that encodes genetic information. Dna is a double-stranded molecule held together by we
Deoxyribose: A type of sugar that is one component of dna (deoxyribonucleic acid).
Diploid: A full set of genetic material, consisting of paired chromosomes one chromosome from each parental s
Directed Evolution: A laboratory process used on isolated molecules or microbes to cause mutations and identify subseque
Directed Mutagenesis: Alteration of dna at a specific site and its reinsertion into an organism to study any effects of th
Directed Sequencing: Successively sequencing dna from adjacent stretches of chromosome.
Disease: Any deviation from the normal structure or function of any part, organ, or system of the body that i
Disease-Associated Genes: Alleles carrying particular dna sequences associated with the presence of disease.
Dmd: Duchenne muscular dystrophy.
DNA Bank: A service that stores dna extracted from blood samples or other human tissue.
DNA Fingerprint Technique: A method employed to determine differences in amino acid sequences between related proteins: relies
DNA Hybridization: A technique for selectively binding specific segments of single-stranded (ss) dna or rna by base pai
DNA Probe: Any biochemical used to identify or isolate a gene, a gene product, or a protein.
DNA Repair Genes: Genes encoding proteins that correct errors in dna sequencing.
DNA Replication: The use of existing dna as a template for the synthesis of new dna strands. In humans and other euka
DNA Sequence: The relative order of base pairs, whether in a fragment of dna, a gene, a chromosome, or an entire g
DNA Sequencing: Plus and minus or 'primed synthesis' method, developed by sanger, dna is synthesized in vitro in suc
Domain: A discrete portion of a protein with its own function. The combination of domains in a single protei
Dominant: Alleles that determine the phenotype displayed in a heterozygote with another (recessive) allele.
Double Helix: The twisted-ladder shape that two linear strands of dna assume when complementary nucleotides on opp
Down Syndrome: A type of mental deficiency due to trisomy (three copies) of autosome 21, a translocation of 21 or m
Draft Sequence: The sequence generated by the hgp as of june 2000 that, while incomplete, offers a virtual road map
Duchenne-Becker Muscular Dystrophy: The most common and severe form of muscular dystrophy: transmitted as an x-linked trait. X-linked re
Dwarfism: Conditions of short stature with adult height under 4'10' as adult, usually with normal intelligence
Dystonia: Neurologic condition involving repeated twisting and movement. Involves a variety of muscle groups.
E Coli: Common bacterium that has been studied intensively by geneticists because of its small genome size,
Electrophoresis: A method of separating large molecules (such as dna fragments or proteins) from a mixture of similar
Electroporation: A process using high-voltage current to make cell membranes permeable to allow the introduction of n
Embryonic Stem (ES) Cells: An embryonic cell that can replicate indefinitely, transform into other types of cells, and serve as
Endonuclease: An enzyme that cleaves its nucleic acid substrate at internal sites in the nucleotide sequence.
Endonuclease Restriction Enzyme: A protein that recognizes specific, short nucleotide sequences and cuts dna at those sites. Bacteria
Enzyme: A protein that acts as a catalyst, speeding the rate at which a biochemical reaction proceeds but no
Epistasis: One gene interfers with or prevents the expression of another gene located at a different locus.
Erythrocytes: The hemoglobin-containing cell found in the blood of vertebrates.
Escherichia Coli: Common bacterium that has been studied intensively by geneticists because of its small genome size,
Ethics: The study of fundamental principles which defines values and determines moral duty and obligation.
Euchromatin: The chromatin that shows the staining behavior characteristic of the majority of the chromosomal com
Eugenics: The improvement of humanity by altering its genetic composition by encouraging breeding of those pre
Eukaryote: Cell or organism with membrane- bound, structurally discrete nucleus and other well- developed subce
Eukaryote: Cell or organism with membrane- bound, structurally discrete nucleus and other well- developed subce
Exogenous DNA: Dna originating outside an organism that has been introducted into the organism.
Exons: Portion of a gene included in the transcript of a gene and survives processing of the rna in the cel
Exonuclease: An enzyme that cleaves nucleotides sequentially from free ends of a linear nucleic acid substrate.
Expressed Sequence Tag (EST): A short strand of dna that is a part of a cdna molecule and can act as identifier of a gene. Used in
Fetal Alcohol Syndrome: A link between excessive alcohol consumption during pregnancy and birth defects: characteristics inc
Filial Generation (F1-F2): Each generation of offspring in a breeding program, designated f1, f2, etc.
Fingerprinting: In genetics, the identification of multiple specific alleles on a person's dna to produce a unique i
Finished DNA Sequence: High-quality, low error, gap-free dna sequence of the human genome. Achieving this ultimate 2003 hgp
Flow Cytometry: Analysis of biological material by detection of the light- absorbing or fluorescing properties of ce
Flow Cytometry: Analysis of biological material by detection of the light- absorbing or fluorescing properties of ce
Flow Karyotyping: Use of flow cytometry to analyze and separate chromosomes according to their dna content.
Fluorescence In Situ Hybridization (FISH): A physical mapping approach that uses fluorescein tags to detect hybridization of probes with metaph
Forensics: The use of dna for identification. Some examples of dna use are to establish paternity in child supp
Fragile Sites: A non-staining gap of variable width that usually involves both chromatids and is always at exactly
Fragile-X Syndrome: X-linked trait: the second most common identifiable cause of genetic mental deficiency.
Fraternal Twin: Siblings born at the same time as the result of fertilization of two ova by two sperm. They share th
Full Gene Sequence: The complete order of bases in a gene. This order determines which protein a gene will produce.
Functional Genomics: The study of genes, their resulting proteins, and the role played by the proteins the body's biochem
Gamete: An haploid cell.gel electrophoresis the process by which nucleic acids (dna or rna) or proteins are
GC-Rich Area: Many dna sequences carry long stretches of repeated g and c which often indicate a gene-rich region.
Gene: The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotid
Gene Amplification: Any process by which specific dna sequences are replicated disproportionately greater than their rep
Gene Chip Technology: Development of cdna microarrays from a large number of genes. Used to monitor and measure changes in
Gene Expression: The process by which a gene's coded information is converted into the structures present and operati
Gene Family: Group of closely related genes that make similar products.
Gene Map: The linear arrangement of mutable sites on a chromosome as deduced from genetic recombination experi
Gene Mapping: Determination of the relative positions of genes on a dna molecule (chromosome or plasmid) and of th
Gene Pool: All the variations of genes in a species.
Gene Prediction: Predictions of possible genes made by a computer program based on how well a stretch of dna sequence
Gene Product: The biochemical material, either rna or protein, resulting from expression of a gene. The amount of
Gene Product: The biochemical material, either rna or protein, resulting from expression of a gene. The amount of
Gene Therapy: An experimental procedure aimed at replacing, manipulating, or supplementing nonfunctional or misfun
Gene Transfer: Incorporation of new dna into and organism's cells, usually by a vector such as a modified virus. Us
Genetic Code: The sequence of nucleotides, coded in triplets (codons) along the mrna, that determines the sequence
Genetic Counseling: The educational process that helps individuals, couples, or families to understand genetic informati
Genetic Discrimination: Prejudice against those who have or are likely to develop an inherited disorder.
Genetic Engineering: Altering the genetic material of cells or organisms to enable them to make new substances or perform
Genetic Illness: Sickness, physical disability, or other disorder resulting from the inheritance of one or more delet
Genetic Linkage Map: A chromosome map showing the relative positions of the known genes on the chromosomes of a given spe
Genetic Marker: A gene or other identifiable portion of dna whose inheritance can be followed.
Genetic Mosaic: An organism in which different cells contain different genetic sequence. This can be the result of a
Genetic Polymorphism: Difference in dna sequence among individuals, groups, or populations (e.g., genes for blue eyes vers
Genetic Predisposition: Susceptibility to a genetic disease. May or may not result in actual development of the disease.
Genetic Screening: Testing groups of individuals to identify defective genes capable of causing hereditary conditions.
Genetic Testing: Analyzing an individual's genetic material to determine predisposition to a particular health condit
Genetic Variation: A phenotypic variance of a trait in a population attributed to genetic heterogeneity.
Genetics: The study of the patterns of inheritance of specific traits.
Genome: All of the genes carried by a single gamete: the dna content of an individual, which includes all 44
Genome Project: Research and technology-development effort aimed at mapping and sequencing the genome of human being
Genomic Library: A collection of clones made from a set of randomly generated overlapping dna fragments representing
Genomics: The study of genes and their function.
Genotype: The genetic constitution of an organism, as distinguished from its physical appearance (its phenotyp
Germ Cell: A sex cell or gamete (egg or spermatozoan).haldane equation haldane's law: the generalization that i
Germ Line: The continuation of a set of genetic information from one generation to the next.
Germ Line Gene Therapy: An experimental process of inserting genes into germ cells or fertilized eggs to cause a genetic cha
Guanine (G): A nitrogenous base, one member of the base pair gc (guanine and cytosine) in dna.
Gyandromorph: Organisms that have both male and female cells and therefore express both male and female characteri
Haploid: A single set of chromosomes (half the full set of genetic material), present in the egg and sperm ce
Haplotype: A way of denoting the collective genotype of a number of closely linked loci on a chromosome.
Hardy-Weinberg Law: The concept that both gene frequencies and genotype frequencies will remain constant from generation
Hemizygous: Having only one copy of a particular gene. For example, in humans, males are hemizygous for genes fo
Hemophilia: A sex-linked disease in humans in which the blood-clotting process is defective.
Hereditary Cancer: Cancer that occurs due to the inheritance of an altered gene within a family.
Heterogeneity: The production of identical or similar phenotypes by different genetic mechanisms.
Heterozygosity: The presence of different alleles at one or more loci on homologous chromosomes.
Heterozygote: Having two alleles that are different for a given gene.
High-Throughput Sequencing: A fast method of determining the order of bases in dna.
Highly Conserved Sequence: Dna sequence that is very similar across several different types of organisms.
Homeobox: A short stretch of nucleotides whose base sequence is virtually identical in all the genes that cont
Homolog: A member of a chromosome pair in diploid organisms or a gene that has the same origin and functions
Homologies: Similarities in dna or protein sequences between individuals of the same species or among different
Homologous Chromosome: Chromosome containing the same linear gene sequences as another, each derived from one parent.
Homologous Recombination: Swapping of dna fragments between paired chromosomes.
Homology: Similarity in dna or protein sequences between individuals of the same species or among different sp
Homozygote: Having identical alleles at one or more loci in homologous chromosome segments.
Housekeeping Genes: Those genes expressed in all cells because they provide functions needed for sustenance of all cell
Human Artificial Chromosome (HAC): A vector used to hold large dna fragments.
Human Gene Therapy: Insertion of normal dna directly into cells to correct a genetic defect.
Human Genome Initiative: Collective name for several projects begun in 1986 by doe to create an ordered set of dna segments f
Huntington Disease: A disease characterized by irregular, spasmodic involuntary movements of the limbs and facial muscle
Hybrid: The offspring of genetically different parents.
Hybridization: The process of joining two complementary strands of dna or one each of dna and rna to form a double-
Ichthyosis: Any of several hereditary or congenital skin conditions: skin of affected individuals has a dry, sca
Identical Twin: Twins produced by the division of a single zygote: both have identical genotypes.
Immunotherapy: Using the immune system to treat disease, for example, in the development of vaccines. May also refe
Imprinting: A chemical modification of a gene allele which can be used to identify maternal or paternal origin o
Imprinting: A chemical modification of a gene allele which can be used to identify maternal or paternal origin o
In Situ Hybridization: Use of a dna or rna probe to detect the presence of the complementary dna sequence in cloned bacteri
In Vitro: Studies performed outside a living organism such as in a laboratory.
Incomplete Penetrance: The gene for a condition is present, but not obviously expressed in all individuals in a family with
Independent Assortment: During meiosis each of the two copies of a gene is distributed to the germ cells independently of th
Informatics: The study of the application of computer and statistical techniques to the management of information
Informed Consent: An individual willingly agrees to participate in an activity after first being advised of the risks
Inherit: In genetics, to receive genetic material from parents through biological processes.
Insertion: A chromosome abnormality in which a piece of dna is incorporated into a gene and thereby disrupts th
Intellectual Property Rights: Patents, copyrights, and trademarks.
Interference: One crossover event inhibits the chances of another crossover event. Also known as positive interfer
Interphase: The period in the cell cycle when dna is replicated in the nucleus: followed by mitosis.
Introns: The dna base sequences interrupting the protein- coding sequences of a gene: these sequences are tra
Isochromosome: A metacentric chromosome produced during mitosis or meiosis when the centromere splits transversely
Isoenzyme: An enzyme performing the same function as another enzyme but having a different set of amino acids.
Junk DNA: Stretches of dna that do not code for genes: most of the genome consists of so-called junk dna which
Karyotype: A photomicrograph of an individuals chromosomes arranged in a standard format showing the number, si
Karyotype: A photomicrograph of an individuals chromosomes arranged in a standard format showing the number, si
Kilobase (KB): Unit of length for dna fragments equal to 1000 nucleotides.
Klinefelter Syndrome: An endocrine condition caused by a an extra x-chromosome (47,xxy): characterized by the lack of norm
Knockout: Deactivation of specific genes: used in laboratory organisms to study gene function.
Library: An unordered collection of clones (i.e., cloned dna from a particular organism), whose relationship
Linkage: The proximity of two or more markers (e.g., genes, rflp markers) on a chromosome: the closer togethe
Linkage Disequilibrium: Where alleles occur together more often than can be accounted for by chance. Indicates that the two
Linkage Map: A map of the relative positions of genetic loci on a chromosome, determined on the basis of how ofte
Lligase: An enzyme that functions in dna repair.
Localize: Determination of the original position (locus) of a gene or other marker on a chromosome.
Locus (Pl. Loci): The position on a chromosome of a gene or other chromosome marker: also, the dna at that position. T
Logarithm of the Odd (LOD) Score: A measure of the likelihood of two loci being within a measurable distance of each other.
Long-Range Restriction Mapping: Restriction enzymes are proteins that cut dna at precise locations. Restriction maps depict the chro
Macrorestriction Map: Map depicting the order of and distance between sites at which restriction enzymes cleave chromosome
Mapping Population: The group of related organisms used in constructing a genetic map.
Marfan Syndrome: Autosomal dominant condition of connective tissue: affects the skeletal, ocular and cardiovascular s
Marker: A gene with a known location on a chromosome and a clear-cut phenotype, used as a point of reference
Marker: A gene with a known location on a chromosome and a clear-cut phenotype, used as a point of reference
Mass Spectrometry: An instrument used to identify chemicals in a substance by their mass and charge.
Megabase (MB): Unit of length for dna fragments equal to 1 million nucleotides and roughly equal to 1 cm.
Meiosis: The process of two consecutive cell divisions in the diploid progenitors of sex cells. Meiosis resul
Mendelian Inheritance: One method in which genetic traits are passed from parents to offspring. Named for gregor mendel, wh
Messenger RNA (MRNA): An rna molecular that functions during translation to specify the sequence of amino acids in a nasce
Metaphase: A stage in mitosis or meiosis during which the chromosomes are aligned along the equatorial plane of
Methylation: Addition of a methyl group (-ch3) to dna or rna.
Methylmalonic Acidemia: A group of conditions characterized by the inability to metabolize methylmalonic acid or by a defect
Microarray: Sets of miniaturized chemical reaction areas that may also be used to test dna fragments, antibodies
Microbial Genetics: The study of genes and gene function in bacteria, archaea, and other microorganisms. Often used in r
Microinjection: A technique for introducing a solution of dna into a cell using a fine microcapillary pipet.
Micronuclei: Chromosome fragments that are not incorporated into the nucleus at cell division.
Missense Mutation: A change in the base sequence of a gene that alters or eliminates a protein.
Mitochondrial DNA: The genetic material found in mitochondria, the organelles that generate energy for the cell. Not in
Mitosis: The process of nuclear division in cells that produces daughter cells that are genetically identical
Model Organisms: A laboratory animal or other organism useful for research.
Modeling: The use of statistical analysis, computer analysis, or model organisms to predict outcomes of resear
Molecular Biology: The study of the structure, function, and makeup of biologically important molecules.
Molecular Farming: The development of transgenic animals to produce human proteins for medical use.
Molecular Genetics: The study of macromolecules important in biological inheritance.
Molecular Medicine: The treatment of injury or disease at the molecular level. Examples include the use of dna-based dia
Monogenic Disorder: A disorder caused by mutation of a single gene.
Monosomy: Possessing only one copy of a particular chromosome instead of the normal two copies.
Morbid Map: A diagram showing the chromosomal location of genes associated with disease.
Multifactorial: A characteristic influenced in its expression by many factors, both genetic and environmental.
Multiplexing: A laboratory approach that performs multiple sets of reactions in parallel (simultaneously): greatly
Murine: Organism in the genus mus. A rat or mouse.
Mutagen: An agent that causes a permanent genetic change in a cell. Does not include changes occurring during
Mutagenicity: The capacity of a chemical or physical agent to cause permanent genetic alterations.
Mutation: Any heritable change in dna sequence. Compare polymorphism.
Myotonic Dystrophy: A combination of progressive weakening of the muscles and muscle spasms or rigidity, with difficulty
Neurofibromatosis: One of the most common single gene conditions affecting the human nervous system: in most cases, 'ca
Nitrogenous Base: A nitrogen-containing molecule having the chemical properties of a base. Dna contains the nitrogenou
Nonsense Mutation: A mutation in which a codon is changed to a stop codon, resulting in a truncated protein product.
Noonan Syndrome: A condition characterized by short stature and ovarian or testicular dysfunction, mental deficiency,
Northern Analysis: A technique for transferring electrophoretically resolved rna segments from an agarose gel to a nitr
Northern Blot: A gel-based laboratory procedure that locates mrna sequences on a gel that are complementary to a pi
Nuclear Transfer: A laboratory procedure in which a cell's nucleus is removed and placed into an oocyte with its own n
Nucleic Acid: A large molecule composed of nucleotide subunits.
Nucleolar Organizing Region: A part of the chromosome containing rrna genes.
Nucleotide: A subunit of dna or rna consisting of a nitrogenous base (adenine, guanine, thymine, or cytosine in
Nucleus: The cellular organelle in eukaryotes that contains most of the genetic material.
Oligogenic: A phenotypic trait produced by two or more genes working together.
Oligonucleotide: A molecule usually composed of 25 or fewer nucleotides: used as a dna synthesis primer.
Oncogene: A gene, one or more forms of which is associated with cancer. Many oncogenes are involved, directly
Open Reading Frame (ORF): The sequence of dna or rna located between the start-code sequence (initiation codon) and the stop-c
Operon: A set of genes transcribed under the control of an operator gene.
Osteogenesis Imperfecta: A condition also known as brittle bone disease: characterized by a triangular shaped face with yello
P1-Derived Artificial Chromosome (PAC): One type of vector used to clone dna fragments (100- to 300-kb insert size: average, 150 kb) in esch
Parthenogenesis: The development of an individual from an egg without fertilization.
Patent: In genetics, conferring the right or title to genes, gene variations, or identifiable portions of se
Pedigree: A family tree diagram that shows how a particular genetic trait or disease has been inherited.
Penetrance: The probability of a gene or genetic trait being expressed. 'complete' penetrance means the gene or
Peptide: Two or more amino acids joined by a bond called a 'peptide bond.'
Phage: A virus for which the natural host is a bacterial cell.
Pharmacogenomics: The study of the interaction of an individual's genetic makeup and response to a drug.
Phenocopy: A trait not caused by inheritance of a gene but appears to be identical to a genetic trait.
Phenotype: Observable characteristics of an organism produced by the organism's genotype interacting with the e
Physical Map: A map of the locations of identifiable landmarks on dna (e.g., restriction enzyme cutting sites, gen
Pku: Phenylketonuria, an enzyme deficiency condition characterized by the inability to convert one amino
Plasmid: Autonomously replicating extra-chromosomal circular dna molecules, distinct from the normal bacteria
Plasmid: Autonomously replicating extra-chromosomal circular dna molecules, distinct from the normal bacteria
Pleiotropy: The phenomenon of variable phenotypes for a number of distinct and seemingly unrelated phenotypic ef
Pluripotency: The potential of a cell to develop into more than one type of mature cell, depending on environment.
Polycystic Kidney Disease (PKD): A group of conditions characterized by fluid filled sacs that slowly develop in both kidneys, eventu
Polygenic Disorder: Genetic disorder resulting from the combined action of alleles of more than one gene (e.g., heart di
Polygenic Disorders: Genetic disorders resulting from the combined action of alleles of more than one gene (e.g., heart d
Polymerase: Any enzyme that catalyzes the formation of dna or rna from deoxyribonucleotides or ribonucleotides.
Polymerase (DNA Or RNA): Enzymes that catalyze the synthesis of nucleic acids on preexisting nucleic acid templates, assembli
Polymerase Chain Reaction (PCR): A method for amplifying a dna base sequence using a heat- stable polymerase and two 20- base primers
Polymorphism: Difference in dna sequence among individuals that may underlie differences in health. Genetic variat
Polypeptide: A protein or part of a protein made of a chain of amino acids joined by a peptide bond.
Population Genetics: The study of variation in genes among a group of individuals.
Positional Cloning: A technique used to identify genes, usually those that are associated with diseases, based on their
Prader-Willi Syndrome: A condition characterized by obesity and insatiable appetite, mental deficiency, small genitals, and
Predisposition: To have a tendency or inclination towards something in advance.
Premature Chromosome Condensation (PCC): A method of studying chromosomes in the interphase stage of the cell cycle.
Presymptomatic Diagnosis: Diagnosis of a genetic condition before the appearance of symptoms.
Primer: Short preexisting polynucleotide chain to which new deoxyribonucleotides can be added by dna polymer
Privacy: In genetics, the right of people to restrict access to their genetic information.
Probability: The long term frequency of an event relative to all alternative events, and usually expressed as dec
Proband: Individual in a family who brought the family to medical attention.
Probe: Single- stranded dna or rna molecules of specific base sequence, labeled either radioactively or imm
Prognosis: Prediction of the course and probable outcome of a disease.
Prokaryote: Cell or organism lacking a membrane-bound, structurally discrete nucleus and other subcellular compa
Promoter: A site on dna to which rna polymerase will bind and initiate transcription.
Pronucleus: The nucleus of a sperm or egg prior to fertilization.
Protein: A large molecule composed of one or more chains of amino acids in a specific order: the order is det
Proteome: Proteins expressed by a cell or organ at a particular time and under specific conditions.
Proteomics: The study of the full set of proteins encoded by a genome.
Proteus Syndrome: A condition characterized by distorted asymmetric growth of the body and enlarged head, enlarged fee
Pseudogene: A sequence of dna similar to a gene but nonfunctional: probably the remnant of a once-functional gen
Public Policy: A set of action guidelines or rules that result from the actions or lack of actions of governmental
Purine: A nitrogen-containing, double-ring, basic compound that occurs in nucleic acids. The purines in dna
Pyrimidine: A nitrogen-containing, single-ring, basic compound that occurs in nucleic acids. The pyrimidines in
Radiation Hybrid: A hybrid cell containing small fragments of irradiated human chromosomes. Maps of irradiation sites
Recessive: A gene that is phenotypically manifest in the homozygous state but is masked in the presence of a do
Recessive Gene: A gene which will be expressed only if there are 2 identical copies or, for a male, if one copy is p
Reciprocal Translocation: When a pair of chromosomes exchange exactly the same length and area of dna. Results in a shuffling
Recombinant Clones: Clones containing recombinant dna molecules. See recombinant dna technologies.
Recombinant DNA Molecules: A combination of dna molecules of different origin that are joined using recombinant dna technologie
Recombinant DNA Technology: Procedure used to join together dna segments in a cell-free system (an environment outside a cell or
Recombination: The natural process of breaking and rejoining dna strands to produce new combinations of genes and,
Regulatory Region Or Sequence: A dna base sequence that controls gene expression.
Repeat Sequences: The length of a nucleotide sequence that is repeated in a tandem cluster.
Repetitive DNA: Sequences of varying lengths that occur in multiple copies in the genome: it represents much of the
Resolution: Degree of molecular detail on a physical map of dna, ranging from low to high.
Restriction Enzyme Cutting Site: A specific nucleotide sequence of dna at which a particular restriction enzyme cuts the dna. Some si
Restriction Fragment Length Polymorphism (RFLP): Variation between individuals in dna fragment sizes cut by specific restriction enzymes: polymorphic
Restriction-Enzyme Cutting Site: A specific nucleotide sequence of dna at which a particular restriction enzyme cuts the dna. Some si
Retinitis Pigmentosa: Group of hereditary ocular disorders with progressive retinal degeneration. Autosomal dominant, auto
Retinoblastoma: A childhood malignant cancer of the retina of the eye. Reverse transcriptase viral enzyme used to ma
Retroviral Infection: The presence of retroviral vectors, such as some viruses, which use their recombinant dna to insert
Reverse Transcriptase: An enzyme used by retroviruses to form a complementary dna sequence (cdna) from their rna. The resul
Ribonucleic Acid (RNA): A chemical found in the nucleus and cytoplasm of cells: it plays an important role in protein synthe
Ribose: The five-carbon sugar that serves as a component of rna.
Ribosomal Protein: One of the ribonucleoprotein particles that are the sites of translation.
Ribosomal RNA (RMA): A class of rna found in the ribosomes of cells.
Ribosomes: Small cellular components composed of specialized ribosomal rna and protein: site of protein synthes
Risk Communication: In genetics, a process in which a genetic counselor or other medical professional interprets genetic
Rubinstein-Taybi Syndrome: Condition with multiple congenital anomalies including: mental deficiency, broad thumbs, small head,
Sanger Sequence: Plus and minus or 'primed synthesis' method: dna is synthesized so it is radioactively labeled and t
Sanger Sequencing: A widely used method of determining the order of bases in dna.
Satellite: A chromosomal segment that branches off from the rest of the chromosome but is still connected by a
Scaffold: In genomic mapping, a series of contigs that are in the right order but not necessarily connected in
Segregation: The normal biological process whereby the two pieces of a chromosome pair are separated during meios
Selection: The process of determining the relative share allotted individuals of different genotypes in the pro
Sequence Assembly: A process whereby the order of multiple sequenced dna fragments is determined.
Sequence Tagged Site (STS): Short (200 to 500 base pairs) dna sequence that has a single occurrence in the human genome and whos
Sequencing: Determination of the order of nucleotides (base sequences) in a dna or rna molecule or the order of
Sequencing Technology: The instrumentation and procedures used to determine the order of nucleotides in dna.
Sex Chromosome: The x or y chromosome in human beings that determines the sex of an individual. Females have two x c
Sex Determination: The mechanism in a given species by which sex is determined: in many species sex is determined at fe
Sex-Linked: Traits or diseases associated with the x or y chromosome: generally seen in males.
Shotgun Method: Sequencing method that involves randomly sequenced cloned pieces of the genome, with no foreknowledg
Sickle Cell Anemia: An hereditary, chronic form of hemolytic anemia characterized by breakdown of the red blood cells: r
Single Nucleotide Polymorphism (SNP): Dna sequence variations that occur when a single nucleotide (a, t, c, or g) in the genome sequence i
Single-Gene Disorder: Hereditary disorder caused by a mutant allele of a single gene (e.g., duchenne muscular dystrophy, r
Somatic Cell: Any cell in the body except gametes and their precursors.
Somatic Cell Gene Therapy: Incorporating new genetic material into cells for therapeutic purposes. The new genetic material can
Somatic Cell Genetic Mutation: A change in the genetic structure that is neither inherited nor passed to offspring. Also called acq
Somatic Cell Hybrid: Hybrid cell line derived from two different species: contains a complete chromosomal complement of o
Somatic Cells: Any cell in the body except gametes and their precursors.
Somatic Mutation: A mutation occurring in any cell that is not destined to become a germ cell: if the mutant cell cont
Southern Blotting: A technique for transferring electrophoretically resolved dna segments from an agarose gel to a nitr
Spectral Karyotype (SKY): A graphic of all an organism's chromosomes, each labeled with a different color. Useful for identify
Spina Bifida: A congenital condition that results from altered fetal development of the spinal cord, part of the n
Splice Site: Location in the dna sequence where rna removes the noncoding areas to form a continuous gene transcr
Sporadic Cancer: Cancer that occurs randomly and is not inherited from parents. Caused by dna changes in one cell tha
Stem Cell: Undifferentiated, primitive cells in the bone marrow that have the ability both to multiply and to d
Structural Genomics: The effort to determine the 3d structures of large numbers of proteins using both experimental techn
Substitution: In genetics, a type of mutation due to replacement of one nucleotide in a dna sequence by another nu
Suppressor Gene: A gene that can suppress the action of another gene.
Syndrome: A recognizable pattern or group of multiple signs, symptoms or malformations that characterize a par
Syngeneic: Genetically identical members of the same species.
Synteny: Genes occurring in the same order on chromosomes of different species.
Tandem Repeat Sequences: Multiple copies of the same base sequence on a chromosome: used as markers in physical mapping.
Targeted Mutagenesis: Deliberate change in the genetic structure directed at a specific site on the chromosome. Used in re
Tay-Sachs Disease: A fatal degenerative disease of the nervous system due to a deficiency of hexosamidase a, causing me
Technology Transfer: The process of converting scientific findings from research laboratories into useful products by the
Telomerase: The enzyme that directs the replication of telomeres.
Telomere: The ends of chromosomes. These specialized structures are involved in the replication and stability
Teratogenic: Substances such as chemicals or radiation that cause abnormal development of a embryo.
Teratogens: Any agent that raises the incidence of congenital malformations.
Thymine (T): A nitrogenous base, one member of the base pair a- t (adenine- thymine).
Toxicogenomics: The study of how genomes respond to environmental stressors or toxicants. Combines genome-wide mrna
Trait: Any detectable phenotypic property of an organism.
Transcription: The synthesis of an RNA copy from a sequence of DNA (a gene): the first step in gene expression.
Transcription Factor: A protein that binds to regulatory regions and helps control gene expression.
Transcriptome: The full complement of activated genes, mrnas, or transcripts in a particular tissue at a particular
Transduction: The transfer of bacterial genetic material from one bacterium to another using a phage as a vector.
Transfection: The introduction of foreign dna into a host cell.
Transfer RNA (TRNA): A class of rna having structures with triplet nucleotide sequences that are complementary to the tri
Transferase: Enzymes that catalyze the transfer of functional groups between donor and acceptor molecules.
Transformation: A process by which the genetic material carried by an individual cell is altered by incorporation of
Transgenic: An experimentally produced organism in which dna has been artificially introduced and incorporated i
Transgenic Organism: One into which a cloned genetic material has been experimentally transferred, a subset of these fore
Translation: The process in which the genetic code carried by mrna directs the synthesis of proteins from amino a
Translocation: A chromosome aberration which results in a change in position of a chromosomal segment within the ge
Transposable Element: A class of dna sequences that can move from one chromosomal site to another.
Triplet Code: A code in which a given amino acid is specified by a set of three nucleotides.
Trisomy: Possessing three copies of a particular chromosome instead of the normal two copies.
Tumor Suppressor Gene: Genes that normally function to restrain the growth of tumors: the best understood case is for hered
Unesco: United national educational, scientific, and cultural organization.
Uracil: A nitrogenous base normally found in rna but not dna: uracil is capable of forming a base pair with
Variable Number Tandem Repeats (VNTR): Any gene whose alleles contain different numbers of tandemly repeated oligonucleotide sequences.
Vector: A self-replicating dna molecule that transfers a dna segment between host cells.
Virus: A noncellular biological entity that can reproduce only within a host cell. Viruses consist of nucle
Von Hippel-Lindau Syndrome: An autosomal dominant condition characterized by the anomalous growth and proliferation of blood ves
Western Blot: A technique used to identify and locate proteins based on their ability to bind to specific antibodi
Western Blotting Analysis: A technique used to identify a specific protein: the probe is a radioactively labeled antibody raise
Wild Type: The form of an organism that occurs most frequently in nature.
X Chromosome: One of the two sex chromosomes, x and y.
X-Inactivation: The repression of one of the two x-chromosomes in the somatic cells of females as a method of dosage
Xenograft: Tissue or organs from an individual of one species transplanted into or grafted onto an organism of
XYY Syndrome: Genetic condition in males with extra y chromosome (in 1 in 1000 male births). Symptoms: tall statur
Y Chromosome: One of the two sex chromosomes, x and y.
Yeast Artificial Chromosome (YAC): A vector used to clone dna fragments (up to 400 kb): it is constructed from the telomeric, centromer
Zinc-Finger Protein: A secondary feature of some proteins containing a zinc atom: a DNA-binding protein.
Zoo Blot: northern analysis of mRNA from different organisms.

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