Mendelian Inheritance Flashcards
Autosomal dominant
A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes. Ex. Huntington disease
Allele
One of the alternative versions of a gene or DNA sequence at a given locus
Autosomal recessive
A pattern of inheritance in which an affected individual has two copies of the mutant gene. Ex. Cystic fibrosis
Codominant
If both alleles of a pair are expressed in the heterozygous state then the alleles (and or traits determined by them) are codominant
Compound heterozygote
an individual or genotype with two different mutant alleles at the same locus
Consanguineous
Related by descent from a common ancestor
Expressivity
The extent to which a genetic defect is expressed. If there is variable expressivity, the trait may vary in expression from mild to severe but is never completely unexpressed in individuals who have the corresponding genotype. Contrast this topic with that of penetrance
Founder effect
A high frequency of a mutant allele in a population founded by a small ancestral group when one or more of the founders was a carrier of the mutant allele
Genetic anticipation
The progressively earlier onset and increased severity of certain diseases in successive generations of a family. Anticipation is caused by expansion of the number of unstable repeats within the gene responsible for the disease
Genotype
The genetic constitution f of an individual as distinguished from the phenotype. More specifically, the alleles present at one locus
Heterozygous
An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes
Homozygous
An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes
Locus
The position occupied by a gene on a chromosome. Different forms of the gene (alleles) may occupy the locus
Mutation
Any permanent heritable change in the sequence of genomic DNA
Penetrance
The fraction of individuals with a genotype known to cause a disease who have any signs or symptoms of the disease. Contrast with expressivity
Phenotype
The observed biochemical, physiological, and morphological characteristics of an individual, as determined by his or her genotype and the environment in which it is expressed. Also, in a more limited sense, the abnormalities resulting from a particular mutant gene
Polygenic inheritance
Inheritance determined by many genes at different loci with small additive effects; not to confused with multifactorial inheritance, in which environmental as well as genetic factors may be involved
Pro band
The affected family member through whom the family is ascertained
Random mating
In a randomly mating population, the frequencies of the various makings between individuals with particular genotypes are determined solely by the frequencies of the alleles concerned
X-linked dominant
Genetic inheritance by which a dominant gene is carried on the X chromosome. A gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder
X-linked recessive
Genetic inheritance in which a mutation in a gene on the X chromosome causes the phenotype of the expressed (1) in males (necessarily hemizygous for the gene mutation because they only have one X chromosome) (2) in females (homozygous for the gene mutation: they have one copy of the gene mutation on each of their two X chromosomes)
