Correlagen Glossary of Genetic Terms

Glossary of Genetic Terms

Amplicon	Unit of DNA amplified by PCR using one set of primers

Autosomal	Referring to any chromosome other than the sex-determining chromosomes; of note, an autosomally inherited phenotype typically affects males and females equally.

Carrier	A heterozygote for a recessive pathogenic sequence variant; a carrier is not affected with the phenotype associated with the pathogenic sequence variant.

De novo	Newly arisen; not inherited

Dominant	Associated with a phenotype in a dominant mode of inheritance; a dominantly inherited phenotype is expressed if a pathogenic sequence variant is located on at least one copy of a given chromosome.

Exons	Segments of gene sequence that are present in a mature mRNA

Frameshift mutation	A DNA sequence variation that results in a shift of the reading frame during translation of the mRNA; such a frameshift usually causes a dramatic change in the amino acid sequence of the encoded protein downstream of the mutation and often leads to premature termination of translation, as stop codons are enriched in non-coding reading frames.

Genotype	The genetic makeup of an individual

Germline mosaicism	If a sequence variant arose during an individual's prenatal or postnatal development, affecting a germline cell or a germline precursor cell, it is present only in the clonal descendants of the cell in which the mutation event occurred. In other words, the individual is a mosaic of germline cells with the sequence variant and germline cells without the sequence variant.

Hemizygote	An individual who harbors a particular DNA sequence on a chromosome that is present in only one copy

Hemizygous	If used for an individual: harboring a particular DNA sequence on a chromosome that is present in only one copy. If used for a sequence variant: occurring on a chromosome that is present in only one copy

Heterozygote	An individual who harbors a particular DNA sequence on only one of two copies of a given chromosome

Heterozygous	If used for an individual: harboring a particular DNA sequence on only one of two copies of a given chromosome. If used for a sequence variant: occurring on only one of two copies of a given chromosome

Homozygote	An individual who harbors a particular DNA sequence on both copies of a given chromosome

Homozygous	If used for an individual: harboring a particular DNA sequence on both copies of a given chromosome. If used for a sequence variant: occurring on both copies of a given chromosome

Introns	Segments of gene sequence that are removed from full-length RNA transcript ( pre-mRNA) through splicing during mRNA maturation

Missense mutation	A DNA sequence variation that results in substitution of one amino acid by a different amino acid in the encoded protein

mRNA	messenger RNA; the RNA transcript of the gene sequence that is translated into protein

mRNA isoforms	Different mRNA versions derived from full-length RNA transcripts of the same gene sequence through alternative splicing

Nonsense mutation	A DNA sequence variation that results in substitution of an amino acid by a stop codon, leading to truncation of the encoded protein at the site of the mutation

Phenotype	The physical and physiological appearance of an individual as a result of expression of a particular gene

Pseudoautosomal	Referring to a region present on both the X and the Y chromosome that is subject to recombination between the X and the Y chromosome; on the X chromosome, the pseudoautosomal region escapes somatic transcriptional inactivation.

Recessive	Associated with a phenotype in a recessive mode of inheritance; a recessively inherited phenotype is only expressed if pathogenic sequence variants are located on both copies of a given chromosome. Since males harbor only one X chromosome, X-linked recessive phenotypes are always expressed in males.

Sequence variant	Any change in the gene sequence relative to the human genome reference sequence. Correlagen uses as reference sequence the sequence published by UCSC Genome Bioinformatics in March of 2006 (hg18)

Splice site	Highly conserved intronic sequences near exon/intron and intron/exon junctions necessary for correct removal of introns from the pre-mRNA

Splice variant	A DNA sequence variation that results in incorrect splicing of a newly transcribed pre-mRNA

Splicing	Removal of introns from the newly transcribed pre-mRNA

Somatic	Referring to any non-germline cell

Somatic mosaicism	If a sequence variant arose during an individual's prenatal or postnatal development, affecting a somatic cell, it is present only in the clonal descendants of the cell in which the mutation event occurred. In other words, the individual is a mosaic of somatic cells with the sequence variant and somatic cells without the sequence variant.

Synonymous mutation	A DNA sequence variation that does not result in a change in the amino acid sequence of the encoded protein; also known as silent mutation

X-linked	Located on the X chromosome; of note, an X-linked phenotype showing recessive inheritance in females affects predominantly males, since X-linked recessive phenotypes are always expressed in males.

Y-linked	Located on the Y chromosome