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.

Chorionic villus sampling : Method of prenatal diagnosis consists in a chorionic villus sampling; it can be performed between 10° and 12° pregnancy week.

Combined test

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).

Cystic fibrosis

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.

Dominant autosomal transmission

Double Y Syndrome

Down Syndrome

Edwards Syndrome

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 deafness

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.

Hereditary trombophilia

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.

Klinefelter Syndrome

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.

Nucleotide constitutional element of : DNA, compounded by sugar called deoxyribose, a phosphate group and nitrogenous bases.


Patau Syndrome

Paternity (see Paternity Test)

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.

Pendred Syndrome

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.

Recessive autosomal transmission

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.

Sex-linked transmission

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.

Triple X Syndrome

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).

Turner Syndrome

Turner Syndrome

Tymine: Nitrogenous base of DNA (sign T).

Uracil: Nitrogenous base of RNA (sign U).

Variation: synonym of polymorphism.

X-Fragile Syndrome

Zygote: Fertilized ovum that dividing it originates embryo.