Adenine: Nitrogenous base of DNA (sign A).
Allele: Alternative gene form (e.g. wild type allele or mutated allele).
alpha-fetoprotein: is the most abundant plasma protein found in the human fetus, increasing in pregnancy if the fetus is affected by neural tube difects (spinal bifida,..) or decreasing if the fetus has a trisomy 21 (Down syndrome).
Amino acid: Organic compound, part of a protein.
Amniocentesis: Prenatal diagnostic method consists in a amniotic liquid sampling and fetal cells included; it can be performed from the 16° pregnancy week.
Aneuploidy: numerical alteration of chromosomal set.
Autosome: not sexual chromosome (in human being there are 22 autosomal chromosome).
Band: Chromosomal region in a more pale or dark colours compared to next regions highlight after particular banding methods. There are different kind of bands (GTG, Q, R, C, …).
Carrier: Male or Female individual, heterozygous for a mutation in a gene that not shows the pathology (asymptomatic).
Chromosome: packaged and organized structure located in the cellular nucleus, containing DNA: the human being has 46 chromosomes, divided in 23 couples.
Chorionic villi (Trophoblast): Tessue enveloping the embryo at the beginning of pregnancy and starting from 12° week it originates placenta.
Compound heterozygous: Individual affected by an autosomal recessive pathology caused by a couple of alleles of a specific gene with different mutation
Cordocentesis (see Fetal Blood analysis).
Cytosine: Nitrogenous base of DNA (sign C).
Deletion: Chromosomal aberration due to a loss of a chromosomal region.
Deoxyribonucleic acid (see DNA)
DNA: Acronym of Deoxyribonucleic acid: molecule located in chromosomes, containing a genetic information to produce RNA and proteins; its chemical structure is compounded by sugar called deoxyribose, a phosphate group and nitrogenous bases.
Dominant (character): Character (physical, biochemical and physiological aspect), expressed in heterozygous individuals.
Exon: Genic region not removed during transcription process, containing the informations (code) for the synthesis of a specific protein.
Fetal blood analysis: Prenatal diagnosis method of fetal blood sampling from umbilical cord; it can be performed from 18° week until the end of pregnancy.
Gene: DNA segment containing the instruction for the synthesis of a specific protein.
Genetic code: DNA instructions like succession of nitrogenous bases (es. ATTACCGGC….) for the protein synthesis.
Genetic mosaic: An individual with two or more cellular lines genetically differents, originated by a single zygote .
Genome: set of genes of an individual.
Genotype: genetic constitution o fan individual.
Guanine: Nitrogenous base of DNA (sign G).
Hemizygous: Organism with a only one copy of some genes in own genotype; in the human species it is related on male individuals that have one X chromosome, so they have single copies of X genes.
Heterozygous: Individual with different alleles for a specific gene.
Homozygous: Individual with equal alleles for a specific gene.
Human Papilloma Virus (see HPV)
Intron: Genic region removed during transcription process, so it not encodes aminoacidic sequence of a protein.
Inversion: Chromosomal aberration due to a rotation of 180 ° compared on original orientation.
Karyotype: Tidy chromosomal arrangement inside a cell.
Microdeletion: Loss of chromosomal material, not visible at traditional karyotype exame.
Microsatellites: DNA region constituted by a variable number of in tandem repeats, generally cytosine and adenine (…CACACACACACACACAC…)
Miscarriage: Spontaneus premature interruption of pregnancy due to natural causes or on purpose provoked.
Monosomy: Lack of a chromosome in one of couple of homologous chromosomes. (e.g. X monosomy or Turner syndrome)
Mucoviscidosis (see Cystic fibrosis)
Mutation: Modification of genetic assets for genes and number or structure of a chromosome.
Nitrogenous base: Organic compound with a nitrogen located in the nucleic acids: in the DNA there are four nitrogenous bases: adenine, cytosine, guanine, tymine.
Paternity (see Paternity Test)
PCR: Acronyme of Polymerase Chain Reaction: method of molecular biology to amplify, that is to increase the number of copies, of a specific DNA region.
Phenotype: Physical, biochemical and physiological aspect (or pathological) in an individual causing by interaction between genotype and environment.
Polymorphism (see SNP)
Polymerase Chain Reaction (see PCR)
Prenatal diagnosis: study performer during the pregnancy to verify if the embryo or fetus has inherited a genetic disease.
Protein: Organic complex compound formed by hundred or thousand amino acids. Instructions for the protein synthesis are in the gene.
Recessive (character): Character (Physical, biochemical and physiological or pathological) showed only in homozygous individual.
Reciprocal translocation: Chromosomal structural aberration caused by a rearrangement of chromosomal segments between different chromosomes; it can be unbalanced or balanced if there is or not a loss or gain of genetic material.
Ribonucleic acid (see RNA)
RNA: Acronyme of Ribonucleic acid, a single strand nucleic acid with a sugar ribose instead of deoxyribose and with a uracil instead of a tymine. There are different kind of RNA (messenger, ribosomal, transfer,…) each one with a specific function.
Robertsonian translocation: Chromosomal structural aberration arised by a fusion between acrocentric chromosomes.
Sequence: It is a word refers to DNA to indicate the succession of nitrogenous bases (AAGCGGGTATA…) corresponding a genetic information.
Sequence-Tagged Site (see STS)
Sequencing: Method of molecular biology to identify the sequence of a specific DNA region.
Sequencing technology: Instrument for sequencing one specific DNA fragment.
Spermatogenesis: Maturation process of male gametes in testicle under hormonal stimulus.
SNP: Single Nucleotide Polymorphism, DNA variation in a single nucleotide.
STS: Sequence Tagged Site; small DNA regions (100-500 bp) with known sequence and location. Different STS can be used for many studies, e.g. to identify microdeletions in some genes, such as AZF (AZospermia Factor) on Y chromosome.
Syndrome: Set of clinical sign and symptoms associated with a particulary pathology.
Telomere: Terminal chromosome region.
Transcription: Cellular process throughout which the genetic information is passed on DNA of chromosomes to messenger RNA.
Translation: Cellular process throughout which the genetic information of messenger RNA is translated in protein.
Triploidy: Chromosomal numerical disorder in which there are three of every chromosomes. A human triploid cell has 69 chromosomes.
Trisomy: Chromosomal numerical disorder in which there are a triple copy of a chromosome, e.g. in individuals with a trisomy 21 (Down Syndrome) there are three chromosome 21 instead of normal two.
Trophoblast (see Chorionic villi).
Tymine: Nitrogenous base of DNA (sign T).
Uracil: Nitrogenous base of RNA (sign U).
Variation: synonym of polymorphism.
Zygote: Fertilized ovum that dividing it originates embryo.