Patterns of Single Gene Inheritance Flashcards
What are the Mendelian patterns of inheritance?
- ) Autosomal Recessive
- ) Autosomal Dominant
- ) X-linked recessive
- ) X-linked dominant
What are the three exceptions of Mendelian patterns of inheritance?
- ) Reduced penetrance
- ) Variable Expressivity
- ) Sex-limited phenotypes
Determined primarily by an allele at a single chromosomal locus
-Caused by mutations that occur at a specific location on a locus
Single gene disorders
Single gene disorders are the result of a mutation at a specific locus on the chromosome. These mutations occur on a specific gene and result in a different
Phenotype
One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome
Allele
Set of alleles present at a single locus
-refers primarily to the autosomes
Genotype
Observable expression of the genotype
Phenotype
When the two alleles are the same (i.e. both WT or both mutant)
Homozygous
When one allele is WT and the other allele is a mutation
Heterozygous
When both alleles are mutant, but the mutation are at different locations in the gene
Compound heterozygotes
When an abnormal gene is located on an X chromosome in a male patient
Hemizygous
Distinct mutations in the same gene producing the same phenotype
Allelic Heterogeneity
Distinct mutations in the same gene producing very different phenotypes
Phenotypic heterogeneity
Descibes different mutations in the same gene that can sometimes give rise to strikingly different phenotypes
Phenotypic Heterogeneity
When mutations in more than one gene can cause the same disease
-Ex: Long QT syndrome can be cause by mutations to sodium channels, potassium channels, or structural proteins
Locus Heterogeneity
One gene that affects multiple traits
-Ex: Von Hippel-Lindau Syndrome
Pleiotropy
A single gene defect that affects multiple organs, produces multiple diverse phenotypes, and results in a variety of signs and symptoms
Pleiotropy
When multiple genes affect one trait
-Ex: Hair loss
Polygenic
Mutations at different loci that produce the same phenotype
Locus Heterogeneity
Affect 1:300 neonates and are responsible for 7% of pediatric hospitalizations
Single gene disorders
Most single gene disorders follow a pattern of
Mendelian Inheritance
Follow classic inheritance patterns and occurs in fixed and predictable proportions among offspring of specific types of matings
Mendelian Diseases
For Mendelian diseases, you can predict the pattern of inheritance and the genotype from the
Pedigree
Used to establish the pattern of transmission of single gene disorders
-Determined from the family history
Pedigrees