A
Adenine: One of the four bases that make up DNA. Abbreviated with an 'A'.
Amniocentesis: A procedure preformed during the 15th week of pregnancy or later to collect material for prenatal testing. A slender needle is inserted into the woman's abdomen and into the uterus and amniotic fluid from around the fetus is withdrawn.
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B
Base: A small molecule inside the larger molecule of DNA. Bases - A, C, G, and T - are arranged in line in a DNA molecule (e.g. CGGTACAGG) and encode instructions for making proteins.
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C
Carrier: A person that carries a gene that causes a disorder, but does not show symptoms.
Chorionic villus sampling (CVS): A procedure performed between 10 and 12 weeks after a woman's last menstrual period to collect material for prenatal testing. A needle is used (abdominally) or a catheter is inserted (cervically) into the substance of the placenta but staying outside the amniotic sac.
Chromosome: Chromosomes are packages of DNA found in the nucleus of cells. Humans have 46 chromosomes.
Cytosine: One of the four bases that make up DNA. Abbreviated with a 'C'.
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D
DNA: Short for deoxyribonucleic acid, DNA is the molecule that carries genetic information.
Dominant: Refers to genetic disorders in which a person only needs one copy of the mutated gene to develop the disorder.
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E
Embryo: A developing human from the time of implantation to the end of the eighth week after conception.
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F
Fetus: A developing human from usually three months after conception to birth.
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G
Gamete: A mature sex cell, either sperm or egg. In sexual reproduction, gametes have half the total number of chromosomes of the organism (haploid state);a fusion of two gametes provides a complete set of chromosomes (diploid state).
Gene: A portion of DNA that contains instructions for making a protein.
Genetic Counseling: A short-term educational counseling process for individuals and families who have a genetic disease or who are at risk for such a disease. Genetic counseling provides patients with information about their condition and helps them make informed decisions.
Genotype: The genetic composition of a person. Usually used when considering one gene or chromosome (e.g., males have a XY genotype, females have a XX).
Guanine: One of the four bases that make up DNA. Abbreviated with a 'G'.
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H
Heparin: A molecule found especially in the liver, used as an anti-coagulant, to delay the blood clotting process.
Hypothyroidism: A condition characterized by lowered metabolic rate and general loss of vigor caused by deficient activity of the thyroid gland.
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K
Karyotype: The chromosomal complement of an individual, including the number of chromosomes and any abnormalities. The term is also used to refer to a photograph of an individual's chromosomes.
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L
Lymphocytes: A small white blood cell that plays a major role in defending the body against disease. There are two main types of lymphocytes: B cells, which make antibodies that attack bacteria and toxins, and T cells, which attack body cells themselves when they have been taken over by viruses or become cancerous.
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M
Meiosis: The process of cell division during which gametes, sex cells, are made. Meiosis is a reduction process as the chromosome number of the final products is reduced from a full complement to one half.
Metaphase: A stage during cell division when the chromosomes align along the center of the cell. Because metaphase chromosomes are highly condensed, scientists use these chromosomes for gene mapping and identifying chromosomal aberrations.
Mitosis: The process of cell division during which somatic cells are made. In mitosis, one cell divides evenly to produce two daughter cells that have the same chromosome number.
Mosaicism: The condition where an organism has cells with different genetic makeup.
Mutation: A change in the genetic code (the A's, C's, G's and T's) of a gene.
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N
Non-disjunction: Refers to the uneven separation of chromosomes during cell division. When non-disjunction occurs, one of the daughter cells of the division will have an extra chromosome, the other daughter cell will have one less.
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P
Percutaneous Umbilical Blood Sampling (PUBS) : A procedure that draws fetal blood for testing. A needle is inserted into the mother's abdomen and blood is drawn from the umbilical vein of the umbilical cord.
Protein: A type of molecule produced by the body. The instructions for producing proteins reside in the genes.
Punnett square: A method of showing the potential offspring of two parents.
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R
Recessive: Refers to genetic disorders in which a person must have two copies of the mutated gene to develop the disorder.
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T
Translocation: Breakage of a large segment of DNA from one chromosome, followed by the segment's attachment to a different chromosome.
Trisomy: Possessing three copies of a particular chromosome instead of the normal two copies.
Thymine: One of the four bases that make up DNA. Abbreviated with a 'T'.
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Z
Zygote: Refers to the cell formed by the union of two gametes; more broadly, refers to the organism that develops from such a cell.
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