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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

 

 
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