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Glossary
Amniocytes AneuVysion Test Centromere Chorionic Villus Sampling (CVS) Chromosome Chromosome Abnormalities Cytogeneticist DNA DNA Probe Down syndrome Fluorescence in situ Hybridization (FISH) Gene Gene amplification Genotype Human Genome Human Genome Project Hybridization (e.g., DNA hybridization) in situ Karyotyping (standard) Klinefelter Syndrome Oncogene Triple Screen Trisomy Trisomy 13 Trisomy 18 Trisomy 21 Turner Syndrome Ultrasonography Amniocentesis
A procedure typically performed near the 16th week of pregnancy to test for fetal abnormalities. Amniotic fluid (which contains fetal cells) is withdrawn by syringe and needle from the amniotic sac surrounding the fetus. Amniocytes
Cells shed by the developing fetus and found in the surrounding amniotic fluid. AneuVysion Test
A prenatal diagnostics assay that analyzes chromosome 13, 18, 21, X and Y for abnormal copy numbers in fetal (amniotic fluid) cells. Utilizing Vysis Fluoresence in situ Hybridization (FISH) technology, the assay provides test results in 24 to 48 hours. Centromere
The constricted region usually near the center of a chromosome (at the joining point of chromosome arms) consisting of highly repeated DNA sequences. Chorionic Villus Sampling (CVS)
A procedure performed via the cervix between the 10th and 12th week of pregnancy to detect genetic defects in the fetus. Cells taken from the chorion - a layer of embryonic tissue surrounding the fetus - are analyzed. Chromosome
Structure in a cell on which genes are located, consisting of a highly compacted stretch of DNA with associated proteins.
Chromosome Abnormalities
These can be either structural or numerical. Structural abnormalities include translocations, deletions or insertions, duplications and amplifications. Numerical abnormalities are either a gain or loss of chromosomes. Cytogeneticist
One who studies human chromosomes and their abnormalities. DNA
An acronym for deoxyribonucleic acid. DNA contains all the information necessary for any organism to develop and function. The four chemical building blocks of DNA are Adenine, Thymine, Cytosine and Guanine. DNA Probe
A segment of DNA specifically designed to be complementary to a target sequence of chromosomes, genes or gene sequences. For FISH, the synthetic piece of DNA is coupled with a fluorescent indicator, or tag, so that the chromosomes or genes it binds (or hybridizes) to can be directly visualized. Down syndrome
A congenital disease usually caused by an extra copy of chromosome 21 (trisomy 21). Fluorescence in situ Hybridization (FISH)
A technique utilizing a fluorescent-labeled DNA probe to detect a particular chromosome or gene.
Gene
A specific, unique stretch of DNA sequence that codes for a single characteristic or component of physical development and function. Gene amplification
Increase in the normal copy number of a gene. Genotype
The genetic composition of an organism. In human karyotyping, the genotype is designated 46, XX for normal females and 46, XY for normal males. (46 refers to the total number of chromosomes: one pair of each chromosome numbers 1 through 22 plus a pair of sex chromosomes, X and Y). Human Genome
The complete set of human genes - approximately 40,000 total - which together contain information covering inherited aspects of human physical development and function. Human Genome Project
Begun in 1990, it aims to identify, map, sequence and interpret all of the estimated 40,000 human genes, producing a vast database of human genetic information. Hybridization (e.g., DNA hybridization)
The binding of complementary sequences of DNA through specific base-pairing of Adenine with Thymine and Guanine with Cytosine.
in situ
In the natural or original position Karyotyping (standard)
A visual display of all chromosomes present in a cell, usually by arrangement in matched pairs. Used to detect structural and numerical abnormalities in chromosomes. Klinefelter Syndrome
A genetic abnormality that is caused by an extra X chromosome in a male, and is typically identified as 47, XXY. Oncogene
An abnormal gene that causes a cell to grow in a uncontrolled manner and is responsible for tumor development. Triple Screen
Also referred to as a Multiple Markers Screen. A prenatal diagnostic screen for fetal abnormalities performed between the 16th and 18th week of pregnancy. The test measures the levels of three substances circulating in the mother's blood: alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG) and unconjugated oestriol (uE3). Changes in the levels of these three substances are associated with the presence of Down syndrome or other fetal disorders. Trisomy
A chromosomal abnormality where three copies of a chromosome exist within a cell nucleus.
Trisomy 13
Caused by an extra copy of chromosome 13, which results in multiple birth defects and severe mental retardation. Trisomy 18
A congenital disease caused by an extra copy of chromosome 18. Infants with trisomy 18 rarely survive past six months of age due to multiple birth defects. Trisomy 21
The chromosomal disorder (Down syndrome) caused by an error in cell division that results in an extra copy of chromosome 21. Down syndrome is the most frequent genetic cause of mild to moderate mental retardation. Turner Syndrome
A congenital condition in females designated by a 45,X genotype. Turner syndrome is a genetic abnormality caused by the complete or partial absence of one of the normal two X sex chromosomes. Ultrasonography
A non-invasive diagnostic technique, where sound waves are used to generate an image of the fetus in order to assess its growth and development, and to identify physical abnormalities. For In Vitro Diagnostic Use
The AneuVysion Assay (CEP® 18, X, Y-alpha satellite, LSI® 13 and 21) Multi-color Probe Panel is intended to use CEP 18/X/Y probe to detect alpha satellite sequences in the centromere regions of chromosomes 18, X and Y and LSI 13/21 probe to detect the 13q14 region and the 21q22.13 to 21q22.2 region. The AneuVysion kit is indicated for identifying and enumerating chromosomes 13,18, 21, X and Y via fluorescence in situ hybridization (FISH) in metaphase cells and interphase nuclei obtained from amniotic fluid in subjects with presumed high risk pregnancies. It is not intended to be used as a stand alone assay for making clinical decisions. FISH results are intended to be used as an aid in the diagnosis of numerical abnormalities of chromosomes 13, 18, 21, X and/or Y in conjunction with other information currently used in prenatal diagnosis, consistent with professional standards of practice1. This device is intended for use only with amniocyte cells; it is not intended for and has not been validated for use with other test matrices. This FISH assay will not detect the presence of structural chromosome abnormalities that can also result in birth defects. This FISH assay will be performed in cytogenetic laboratories. 1American College of Medical Genetics (ACMG). Technical and clinical assessment of fluorescence in situ hybridization: an ACMG/ASHG position statement. I. Technical considerations. Genetics in Medicine (2000) 2 6:356-61. |
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