GCP 511 Human Genetics Terms

Allelic heterogeneity

different pathogenic variants in the same gene can cause the same or similar phenotype(s)

Anticipation

the phenomenon where the severity of a genetic disorder increases or the age of onset decreases in successive generations.

Co-dominance

phenotypic expression of both alleles at a locus occurs in a compound heterozygote

Compound heterozygote

inherited two different pathogenic variants

Consaguinity

parents are related by blood

Double heterozygote

inherited two different alleles at two different loci

Incomplete dominance

neither allele is completely dominant over the other, resulting in an intermediate phenotype in the heterozygote

Late age of onset

refers to a condition or trait that manifests later in life, often after reproductive age, and can be influenced by genetic or environmental factors

locus heterogeneity

pathogenic variants in different genes can cause the same or similar phenotype(s)

mosaicism

a condition where an individual has two or more genetically different cell lines, leading to variations in phenotype among different tissues or cell types

new mutation

sporadic occurrence, condition not present in either parent

penetrance

the proportion of individuals with a specific genotype that expresses the associated phenotype

skewed X-inactivation

a phenomenon where one X chromosome in females is preferred over the other in gene expression, leading to unequal gene dosage.

true negative result

a test result indicating no disease when it is indeed absent

Uninformative negative

test result that fails to provide clear information regarding the absence of a disease, often due to insufficient sensitivity.

Variable expressivity

the range of symptoms that may present; the condition is penetrant but varies in severity