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F

false-positive result
A test result that indicates an individual is affected and/or has a certain gene mutation when he or she is actually unaffected and/or does not have the mutation; i.e., a positive test result in a truly unaffected or mutation-negative individual. (NCI Thesaurus)

familial
A phenotype or trait that occurs with greater frequency in a given family than in the general population; familial traits may have a genetic and/or nongenetic etiology.

family history
The genetic relationships within a family combined with the medical history of individual family members. When represented in diagram form using standardized symbols and terminology, it is usually referred to as a pedigree or family tree. (NCI Thesaurus)

FDR
First-degree relative. The parents, siblings, or children of an individual. Also called first-degree relative. (NCI Thesaurus)

first-degree relative
FDR. The parents, siblings, or children of an individual. Also called FDR. (NCI Thesaurus)

FISH
Fluorescence in situ hybridization. A technique used to identify the presence of specific chromosomes or chromosomal regions through hybridization (attachment) of fluorescently-labeled DNA probes to denatured chromosomal DNA. Examination through a microscope under fluorescent lighting detects the presence of the colored hybridized signal (and hence presence of the chromosome material) or absence of the hybridized signal (and hence absence of the chromosome material). Also called fluorescence in situ hybridization. (NCI Thesaurus)

fluorescence in situ hybridization
FISH. A technique used to identify the presence of specific chromosomes or chromosomal regions through hybridization (attachment) of fluorescently-labeled DNA probes to denatured chromosomal DNA. Examination through a microscope under fluorescent lighting detects the presence of the colored hybridized signal (and hence presence of the chromosome material) or absence of the hybridized signal (and hence absence of the chromosome material). Also called FISH. (NCI Thesaurus)

founder effect
A gene mutation observed with high frequency in a population founded by a small ancestral group that was once geographically or culturally isolated, in which one or more of the founders was a carrier of the mutant gene.

frameshift mutation
An insertion or deletion involving a number of base pairs that is not a multiple of three, which consequently disrupts the triplet reading frame of a DNA sequence. Such mutations usually lead to the creation of a premature termination (stop) codon, and result in a truncated (shorter-than-normal) protein product. (NCI Thesaurus)

G

gene
The basic unit of heredity that occupies a specific location on a chromosome. Each consists of nucleotides arranged in a linear manner. Most genes code for a specific protein or segment of protein leading to a particular characteristic or function. (NCI Thesaurus)

genetic counseling
A communication process that seeks to assist affected or at-risk individuals and families in understanding the natural history, disease risks, and mode of transmission of a genetic disorder; to facilitate informed consent for genetic testing when appropriate; to discuss options for risk management and family planning; and to provide for or refer individuals for psychosocial support as needed. The National Society of Genetic Counselors Task Force has also defined the term genetic counseling. (NCI Thesaurus)

genetic heterogeneity
The production of the same or similar phenotypes (observed biochemical, physiological, and morphological characteristics of a person determined by his/her genotype) by different genetic mechanisms. There are two types: (1) allelic heterogeneity – when different alleles at a locus can produce variable expression of a condition; and (2) locus heterogeneity – the term used to describe disease in which mutations at different loci can produce the same disease phenotype.

genetic marker
An identifiable segment of DNA (e.g., Single Nucleotide Polymorphism [SNP], Restriction Fragment Length Polymorphism [RFLP], Variable Number of Tandem Repeats [VNTR], microsatellite) with enough variation between individuals that its inheritance and co-inheritance with alleles of a given gene can be traced; used in linkage analysis. (NCI Thesaurus)

genetic predisposition
Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease. Also called genetic susceptibility. (NCI Thesaurus)

genetic screening
Genetic testing designed to identify individuals in a given population who are at higher risk of having or developing a particular disorder, or carrying a gene for a particular disorder.

genetic susceptibility
Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease. Also called genetic predisposition. (NCI Thesaurus)

genomic imprinting
The process by which one chromosome of a pair is chemically modified, depending on whether the chromosome comes from the father or the mother. These modifications lead to differential expression of a gene or genes on a maternally derived chromosome versus a paternally derived chromosome. (NCI Thesaurus)

germline
The cells from which eggs or sperm (i.e., gametes) are derived.

H

haplotype
A set of closely linked genetic markers present on one chromosome which tend to be inherited together.

heterozygous genotype
Occurs when the two alleles at a particular gene locus are different. A heterozygous genotype may include one normal allele and one mutation, or two different mutations. The latter is called a compound heterozygote.

homozygous genotype
Occurs when both alleles at a particular gene locus are the same. A person may be homozygous for the normal allele or for a mutation.

I

inconclusive
A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called uninformative and indeterminate.

indeterminate
A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called uninformative and inconclusive.

index case
A clinically affected individual through whom attention is first drawn to a genetic disorder in a family.

informative
In genetic testing, a test result that reveals definitively the presence or absence of the germline genetic alteration associated with the hereditary disorder being assessed. In linkage analysis, the ability to distinguish between maternally inherited and paternally inherited DNA markers (polymorphisms) within or near a given gene of interest.

informed consent
A process of information exchange between a clinician and an individual or their legal proxy designed to facilitate autonomous, informed decision making. The informed consent process for genetic testing should include an explanation of the medical and psychosocial risks, benefits, limitations, and potential implications of genetic analysis, a discussion of privacy, confidentiality, the documentation and handling of genetic test results, as well as options for managing the hereditary disease risk. (NCI Thesaurus)

inherited cancer syndrome
Describes the clinical manifestations associated with a mutation conferring cancer susceptibility.

J

No entries.

K

kindred
An extended family.

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