Seminar 3- types of single gene inheritance. traditional and non-traditional inheritance Flashcards
Autosomal dominant inheritance
Mutated gene is a dominant gene located on one of the non-sex chromosomes (autosomes)
Autosomal recessive inheritance
Locus is on an autosome and 2 mutant alleles required for phenotype expression
X-linked dominant inheritance
Locus is on X-chromosome. only 1 mutant allele needed for expression in females
X-linked recessive inheritance
the locus is on x-chromosome and a female must carry both alleles for expression
Autosomal dominant inheritance basic criteria
- All affected children have at least 1 affected parent
- Any child of affected persons has a 50% risk of inheriting
- Unaffected family members don’t transmit the trait to their children
- Trait is not influenced by sex, both sexes likely to have and transmit the trait
Expressions of typical rules of inheritance
Variable expressivity Late onset Pleiotropy Incomplete penetrance Mosaicisms- Gonadal and Somatic De novo mutations
Variable expressivity
Range of signs and symptoms occuring in people with the same genetic condition
- the extent of expressions of the disease phenotype
Pleiotropy
the multiple phenotypic effects of a gene
Incomplete penetrance
Not all people carrying a mutated gene express the associated traits
De novo mutations
present for first time in a family member
- mutation occurs in parents germ cell
Mosaicism
the presence of 2 or more cell lines with diff genotypes in one individual who has developed from a single zygote
- due to error after conception
Gonadal mosaicism
mutation is present in part of a healthy parent’s germ cells
- Osteogenesis imperfecta
- achondroplasia
Somatic mosaicism
mutation occurs in early embryogenesis in a single somatic cell
- Marfan syndrome
- Neurofibromatosis type 1
Examples of autosomal dominant disorders
Marfan syndrome Huntington disease Neurofibromatosis type 1 AD polycystic kidney disease Osteogenesis imperfecta Achondroplasia
Autosomal recessive inheritance criteria
- Both parents are asymptomatic carriers with one normal and mutant allele
- condition typically appears in 1 generation only (siblings)
- 2 carrier parents have a 25% chance of having an affected child
- common in consanguineous marriages
- Each unaffected sibling of the affected individual has a 2/3 chance of being a carrier
