Genetic Inheritance

Genotype

Genetic constitution of an organism.

Phenotype

Physical appearance influenced by genotype and environment.

Allele

Alternative form of a gene.

Autosomal dominant inheritance

Traits expressed in heterozygotes; shows a vertical pattern in pedigrees.

Haploinsufficiency

Disease state where normal physiology requires more than 50% gene product.

Dominant Negative Effect

Abnormal protein interferes with the product of the normal allele.

Reduced penetrance

Proportion of individuals with a given genotype who show the associated phenotype.

Autosomal recessive inheritance

Traits seen only in homozygotes; carriers are heterozygous and unaffected.

Consanguinity

Inbreeding that increases the likelihood of both partners carrying a recessive mutation.

X chromosome inactivation

Random, permanent inactivation of one X chromosome in female cells.

Barr body

Condensed, inactive X chromosome visible as a dark-staining mass.

X-linked recessive inheritance

Diseases rarely expressed clinically in heterozygous females; mainly affects males.

X-linked dominant inheritance

Diseases expressed clinically in many females, lacking male-to-male transmission.

Extranuclear inheritance

Transmission of genetic material located outside the nucleus, such as mitochondrial DNA.

Mitochondrial DNA transmission

Mitochondrial DNA is inherited exclusively via the ovum from the mother.

Heteroplasmy

Presence of a mixed population of normal and mutated mitochondrial DNA.

Genetic drift

Change in gene variant frequency in a population due to random chance.

Gene migration

Introduction of genetic variants from one population to another.

Balanced polymorphism

Maintenance of alleles due to heterozygote advantage like malaria resistance.