3' UTR Downstream region starting after the stop codon of a gene including regulatory sequences for translation termination.
5' UTR Upstream region preceeding a gene. Contains important sequence motifs necessary to regulate the expression if the gene and its tissue and temporal expression.


Allele Alternative form of a gene or a marker at an identical chromosomal position.
Amplification The production of multiple copies of a nucleotide sequence. Can be done synthetically in a test tube by PCR or biologically using a bacterial host.
Antisense strand The noncoding strand of a double stranded DNA-helix.
Ascertainment The selection of individuals for inclusion in a study.
Autosomal Any genetic entity that involves the autosomes.
Autosome Any of chromosomes 1 - 22.


Base Pair (bp) In double stranded DNA the purine-pyrimide complementary pair.
BLOC Group of protein complexes involved in formation and intracellular transport of lysosome-related organelles like lysosomes or melanosomes.
Blot - Northern Transfer of RNA from a gele to a membrane and subsequent hybridization with a gene-specific probe to visualize its transcription product(s) in tissue specific RNA preparations.
Blot - Southern Transfer of restriction digested genomic DNA from a gele to a membrane and subsequent hybridization with a probe of defined chromosomal localization. Southern blots are used to detect RFLPs, VNTRs, or even the presence of a genomic fragment.
Blot - Western Transfer of protein from a gel to a membrane and subsequent probing with an antibody.


Cadherin Domain, extracellular Cadherin domains are extracellular Ca2+-binding domains that mediate binding interaction between cadherin proteins
Cap 7-methylcytosine block of the 5' end of a growing mRNA-chain.
Carrier Individual carrying heterozygously one mutated allele of pair.
Carrier - obligate Daughter of a male being affected with a X-linked disease.
CCAAT-box Sequence at position 75 - 80 bp of most but not all genes. Seems to be necessary for quantification of transcription.
Centimorgan (cM) Unit of a genetic distance used to describe linkage maps. 1 cM equals approximately 1 Mbp and is defined by a recombination probability of 1% between 2 loci.
Chromatide One of the 2 identical double helices of a chromosome.
Chromosome Nucleic acid chains of varying length in the nucleus containing all information besides the mitochondrial genome.
Clone Genetically identical copy of a cell or organism.
Codon Triplet of three nucleotides encoding an amino acid.
Co-Immunoprecipitation Technique to identify interacting proteins by co-transfection of expression vectors in mammalian cell cultures, protein extraction, and cleaning of protein complexes by specific target protein specific antibodies.
Complementary Being counterpart of a matching pair.
Complementary DNA (cDNA) A DNA sequence being complementary to a mRNA sequence. cDNA is the product of reverse transcription from mRNA.
Connecting Cilium Zone between photoreceptor inner and outer segment resembling the structure of a motile cilium but lacking the core structure necessary for motility
Consanguinity (consanguineous) Two people being of the same genetic origin.
Consensus sequence A sequence conserved in a protein or gene denoting a specialized function such as CCAAT-box, TATAA-box, EF-hand etc.
Crossing over Exchange of chromosomal fragments by mechanical crossing of chromatides.Crossing over is the reason of recombination. It happens in meiotic prophase I.


Digenic Genetic condition which is caused by the interplay of two recessive mutations in two genes which are functionally connected.
Diploid A genome consisting of two copies of the complete set of chromosomes.
Dizygous Twins descending from different zygotes.
DNA - genomic Nucleic acid preparation of unprocessed DNA containing the complete genome of an individual.
DNA (Desoxyribonucleic acid) Nucleic acid made from guanine, adenine, thymine, and cytosine. DNA has a desoxyribose/phosphate backbone.
Domain Functional region of a protein establishing catalysis, interaction, or structural features relevant to the protein. Specialized domains often correspond to conserved amino acid sequence motifs.
Dominant Being the expressed allele in a heterozygous condition.


Ecogenetic Resulting from genetic predisposition together with an environmental factor.
Empirical recurrence risk Risk for an offspring or sibling to be affected. The calculation is based on the frequency of the disease in a population in contrast to calculations based on the mode of inheritance of the disease.
Endoplasmatic Reticulum (ER) Cellular compartment to translate proteins. In the ER proteins are prepared and sorted for the distribution among the other cellular compartments.
Enhancer Genetic element placed downstream of a gene to enhance its transcription. Enhancers are part of the promotor and act in cis. Their position varies from gene to gene. There can be more than one enhancer in a promotor.
Euchromatin Light staining regions of the chromosomes in G-banding. Euchromatin is thought to contain the transcriptional active genes.
Euploid Each multiplication of a genome that contains complete multiples of the haploid set of chromosomes.
Exon Parts of gene that are joined to make a mRNA that can be translated into a protein. A gene can be made from one or several exons. Exons at the start and the end of a mRNA can be noncoding but contribute to the regulation of the translation.
Expressivity The amount of effect of a mutation on the phenotype. Variable or reduced expressivity in a dominant trait can cause misinterpretation of the mode of inheritance.


Fingerprint - genetic Individual combination of marker alleles being specific for a single individual.
Founder effect Occurence of a common mutation in a population. The founder effect is caused by a common ancestor who introduced the mutation to the population.
Frameshift mutation A mutation producing an altered reading frame in an mRNA. The resulting amino acid sequence may be shorter or longer but is different to the wildtype due to an altered reading frame causing a premature stop codon.
FRET Fluorescence Resonance Energy Transfer - Behavior of fluorescent dye that gain emission intensity upon transfer of energy from one dye to another.


Gamete Haploid cell resulting from meiosis.
G-banding Giemsa staining of metaphase chromosomes after light trypsin digestion. G-banding is the most currently used banding technique and provides unique banding patterns for each chromosome. The G-banding pattern is used for the assignement of genes.
Gene DNA sequence including a promotor region, exons, introns and a 3' untranslated region encoding a protein.
Gene map - linkage Arrangement of genes on a chromosome based on statistical calculations using recombination data obtained by genetic markers. The linkage distance is given in centimorgan.
Gene map - physical Arrangement of genes on a chromosome based on the nucleotide sequence. The physical distance is given in base pairs.
Genetic code Nucleotide triplets coding for the amino acids and termination signals in protein translation. Frequent amino acids are encoded by more than one triplet (Degeneracy of the genetic code).
Genome Completeness of genetic sequence information of an individual.
Genome - mitochondrial (mt) Circular DNA encoding mitochondrion specific genes including some of the genes for the respiratory chain. The mt-genome resides in the mitochondrion and its genes have no counterpart in the nucleic genome of a cell.
Genotype Combination of alleles of an individual.
Germ line Subset of cells containing the complete genetic information of an individual as provided by the gametes on fertilization. Gonades produce new gametes from the germ line cells.
Gonades Organs producing gametes (ovaries and testes).
Granular osmiophilic deposits Granular osmiophilic deposits in cells in lysosomal storage disorders.


Haploid Single set of chromosomes. Human haploid chromosome set contains 23 chromosomes.
Haplotype Combination of alleles at a given locus of an individual.
Hematoxylin-Eosin Histological technique to counter stain nuclei, cytoplasm, and connecting tissue
Hemizygosity Situation for a X-linked locus in a male genome. There is no counterpart to a X-chromosome allel due to the XY situation of the male genome. Therefore X-linked genes are present in a single copy in the male genome.
Heterochromatin Dark staining regions of the chromosomes in G-banding. Heterochromatin is thought to contain only few genes but contains repetitive elements.
Heterogeneity - allelic Similar or identical phenotypes caused by different mutations of the same gene.
Heterogeneity - genetic Different genetic conditions which cause a single phenotype. Allelic: different mutations of one gene Locus: different genes
Heteroplasmy Variability of fractions of mitochondria carrying mutated gene copies between cells in a tissue or body. Heteroplasmy causes a mosaic of cells varying in expression of a disease gene in a tissue.
Heterosome The sex chromosomes X and Y.
Heterozygosity Situation of a genetic marker showing two different alleles at an autosomal locus.
Heterozygote - compound Affected individual in an autosomal rezessive inheritance carrying two independently mutated alleles of a gene causing the disease.
Homozygosity Situation of a genetic marker showing two equal alleles at an autosomal locus.
Host Bacterium used to amplify a vector.
Housekeeping genes Genes necessary for basic functions of an organism.
Hybridization Basepairing of complementary stretches of single stranded nucleotide sequences.


Intron (IVS) Part of a gene not coding for the gene product. Introns contain regulatory sequences necessary for proper gene transcription. The opinion that introns contain only junk DNA had to be reversed in the recent past.
Inversion Insertion of a nucleotide sequence in reversed direction. Inversion can be small like only a few basepairs or great and visible in chromosome preparations.






Linkage Physical connection between two loci expressed by the probability of an recombination event between them.
Locus Defined position on a chromosome. A locus defines a gene, a polymorphic marker or even a localized piece of nucleotide sequence.
Locus Control Region (LCR) Sequences upstream of a set of co-transcribed genes controlling their interdependence. e.g. RCP/GCP cluster
Lyonization X-chromosome inactivation which occurs randomly in cells for one of the two alleles of a X-linked locus in female heterozygotes. A result of lyonization are mosaics.


Marker Polymorphic sequence of defined chromosomal localisation.
Meiosis Form of cell division that reduces a diploid genome to a haploid genome. Meiosis produces gametes from germ line cells. A central feature of the meiosis is the recombination of genetic information.
Mitosis Form of cell division which distributes the genetic information equally between two somatic cells.
Mode of inheritance The way a disease is transmitted to the offspring. Knowledge of the correct mode of inheritance allows more exact calculations for the risk of recurrence for siblings and offspring and is necessary for significant linkage calculations.
Monozygous Twins descending from the same zygote.
Mosaicism The situation of expression of two alleles of a gene in the same individual. Mosaicism results either from mutations which occur after fertilization and produce two differing cell lines or from alternate inactivation of one of both alleles at a locus.
mRNA (messenger RNA) Processed nucleotide sequence copy of a gene containing uracil instead of thymine. It serves to transport those information of a gene which is necesserary for translation to the ribosomes. mRNA is cleared from all sequences not necessary for translation.
Multifactorial inheritance Genetic condition which is caused by the combination of two or more genes together with several environmental factors.
Mutation Permanent hereditable change in the nucleotide sequence of the genome. Mutations can be pathogenic but do not necessarily need to be.
Mutation - missense A change in the nucleotide sequence of a gene that changes the information of a codon from one amino acid to another.
Mutation - nonsense A change in the nucleotide sequence of a gene that changes the information of a codon from one amino acid to a stop (termination) codon.
Mutation - point A mutation altering a single nucleotide (includes deletion, insertion, base exchange).
Mutation rate The frequency of mutagenic changes for a locus, gamete, or generation.


NHL repeat Found in a variety of enzymes of the copper type II, ascorbate-dependent monooxygenase family which catalyse the C-terminus alpha-amidation of biological peptides. The repeat domain that is often associated with RING finger and B-box motifs
Nonpenetrance Missing expression of a mutation in a carrier.


Oligogenic Phenotype resulting from the interaction of only a few genes.


p-arm Short (petite) arm of a chromosome.
Pathologic Disease causing
PCR - Polymerase Chain Reaction In vitro method to obtain multiple copies of sequence defined by two flanking oligonucleotides using a thermostable DNA-Polymerase.
Penetrance Frequency and extend of a mutation to cause a disease phenotype in a carrier. Given as the proportion of gene carriers that express the phenotype.
periodic acid Schiff reaction Histological staining technique for polysaccharides and glycoproteins
Phenocopy Recurrent disease phenotype in a family or population caused by environmental factors in contrast to a genetic origin.
Phenotype Result of interaction of the gene products and environmental factors.
Plasmid Independently replicating extrachromosomal circular DNA of bacteria carrying additional information like resistance factors or metabolic active genes. Modified plasmids are used in gene technology to transfer, express, or amplify genetic information.
Pleiotropy Effect of a single gene on several organ systems. The effect may be different from tissue to tissue.
Polygenic Phenotype resulting from the interaction of multiple genes.
Polymerase An enzyme that replicates a nucleotide sequence on a nucleotide template.
Polymorphism A mutation that does not cause a functional change in the gene product. The occurrence of more than one allele at a sequence position.
Population A defined group of people. e.g. inhabitants of a village, a region, an island etc.
Primary transcript Direct copy of the coding DNA strand of a gene including exons and introns and missing the mRNA specific modifications like 5' cap and 3' polyadenylation.
Proband Individual of a pedigree used to determine the disease.
Probe Labelled DNA fragment complementary to a defined genetic locus. Used in Southern- and Northern-blot to identified the presence of the sequence of interest.
Promoter Genetic unit in the 5' region of a gene containing transcription regulators like enhancers and silencers to regulate gene activity in a certain environment.
Pseudodominance Fake of dominance in a recessive trait by mating of a homozygous affected with an unaffected heterozygous carrier resulting in affected offspring (like in dominant traits).
Purine Nucleotides Uracil (U), Thymine (T), and Cytosine (C).
Pyrimidine Nucleotides Guanine (G) and Adenosine (A).


q-arm Long arm of a chromosome
qPCR Method to quantify the amount of nucleic acid fragments in a mixed sample of RNA or DNA molecules. Nucleic acid fragments correspond to copies of genes either at the genomic (DNA fragments) or the expression (RNA fragments) level.


Reading frame (open reading frame, ORF) Follow up of nucleotide triplets starting with ATG and ending in TGA, TAA, or TAG (termination codons). If the termination codons are missing it is called an ORF (open reading frame).
Recessive Being the unexpressed allele in a heterozygous condition
Recombination Event of new combination of linked loci in meiosis by crossing over. The probability of an recombination event between two loci decreases by decreased distance of the loci and vice versa.
Recombination fraction Q Amount of recombination events between two loci in a number of meioses. Q is proportional to the distance of the loci.
Recurrence risk The probability of a disease to occur again in a family that has an affected family member.
Restriction enzyme Bacterial enzyme that cleaves doubled stranded DNA at defined positions. A restriction enzyme that cleaves inside a sequence is called an endonuclease.
Restriction map Alignment of restriction sites along a nucleotide sequence.
Restriction site The position at which a restriction enzyme cleaves.
Reverse transcription Transcription of RNA into DNA by use of viral reverse transcriptase.
RFLP - Restriction Fragment Length Polymorphism A mutation causing a nucleotide change which alters an endonuclease recognition site in and outside of genes. RFLP serve as genetic markers in linkage analysis.
RNA (Ribonucleic acid) Nucleic acid made from guanine, adenine, uracil, and cytosine. RNA has a ribose/phosphate backbone.
RNAi Small RNA fragments used to suppress gene expression of genes in vivo.


Saposine Sphingolipid Activator Proteins
Screening - genetic Testing of a set of people for mutations or other genetic conditions to obtain certainty or the risk of affection.
small haiprin RNA RNA molecules forming a hairpin structure. shRNA is used to silence expression by RNA interference.
small interfering RNA Small double stranded RNA molecules used by cells to silence expression of genes and in defense againts viral infections. siRNA is adapted in directed silencing of the expression of dominant negative mutations.
small nuclear Ribo-Nucleo-Protein Set of protein/RNA factors used in RNA splicing
Somatic cell A cell of any tissue in the body besides the gonads.
Splice site Start and end of an intron. The splice site is highly conserved in evolution, up to 100% in the first two nucleotides at the start and end of exons and introns. The adjacent nucleotides contribute to the specificity at different amounts.
Splicing Joining of exons to produce mRNA from primary transcripts.
Splicing defect Mutation of a splice site.
Synteny Physical connection of genes on a chromosome.


Telomere Tips of chromosomes.
Termination codon UAG, UAA, UGA in mRNA sequences causing the translation to stop.
Tetra tricopeptide motif 34 AA motif of proteins involved in nuclear transport or chaperone activity.
Trait - dominant Pedigree in which disease affection is established by the heterozygous state of the affected gene. The pedigree must show transmission from affected to affected.
Trait - recessive Pedigree in which disease affection is established by the homozygous state of the affected gene. The pedigree may show affected siblings but does not show transmission from affected to affected (exception: pseudodominance).
Transcription The synthesis of RNA along a DNA template.
Transgenic Individual that contains foreign DNA in its germ line.
Transition Zone Zone in the photoreceptor inner segment at which the motile elements of the Connecting Cilium are established
Translation Synthesis of proteins along a mRNA template in the ribosomes.


Unfolded Protein Response Cellular mechanism to avoid misfolded and mutated proteins to burden the cell's biochemistry.
Uniparental Disomy Presence of two chromosomes from the same parent in a patient's cells due to rescue mechanisms from trisomy. Trisomy results from missdistributed chromosomes during meiosis.
Untranslated Protein Region 3' and 5' part of an mRNA that is not translated into a protein. (see also 3' UTR and 5' UTR)


Vector Genetic element used to transfer genetic information into a cell. e.g. plasmids or YACs


Wheat Germ Extract Extract of cytosolic fluid from wheat germ cells
Wildtype Any phenotype or genotype that occurs naturally.


X-Chromosome One of the sex chromosomes (see also Y-chromosome) containing genes involved in "X-linked" disorders . Appears as together with another X-chromosome in female individuals.


Y-Chromosome One of the sex chromosomes (see also X-chromosome) containing the information to determine male individuals. Appears as together with an X-chromosome in male individuals.
Yeast Artificial Chromosome Genetic element from yeast that is reduced to its basic replication necessities to obtain capacity for loading with foreign information and use as a vector into the yeast host system.
Yeast-2-Hybrid-Assay Technique to identify interacting proteins by cotransfection of a bait protein gene and a gene library in yeast cells
Yeast-One-Hybrid-Assay Technique to identify proteins binding to promotrs by cotransfection of a vector containing promotor sequence and a gene library in yeast cells


Zygote Diploid cell resulting from fertilization of a female gamete (oocyte) by a male gamete (sperm cell).

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