Lecture 16 Flashcards
Key words
Dominant - Vertical patterns of affected individuals
Recessive - Horizontal patterns of affected individuals
Autosomal recessive - Consanguinity often present between parents
Autosomal - Males and females affected with equal probability
X-linked recessive - Males affected, female carriers
X-linked dominant - All daughters of affected males are affected
Mitochondrial - Non-Mendelian, Maternal inheritance
Autosomal dominant
Every affected individual has an affected biological parent
•Males and females equally likely to be affected
•Recurrence risk of each child of an affected parent is 50%
•Normal siblings do not transmit the trait to their offspring
Autosomal recessive
Males and females equally likely to be affected
•Recurrence risk of each child of an affected parent is 25%
•Trait is characteristically found in siblings, not parents
•Parents of affected children may be related (consanguineous mating)
•Trait may appear as an isolated (sporadic) event
X linked recessive
- Males are much more likely to be affected than females
- Trait is never passed from father to son
- All affected males in a family are related through their mothers
- Passed from an affected grandfather, through his carrier daughters, to half of his grandsons
Mitochondrial
- Non-Mendelian
* Everyone inherits the condition through the maternal line
Complications that affect interpretation of pedigrees
- New mutations
- Penetrance
- Expressivity
- Delayed onset
- Anticipation
- Imprinting
Molecular markers allow mapping:
Phenotypic markers e.g. genetic disorder •Molecular markers e.g. –Structural rearrangements –SNPs –RFLPs –INDELS –Copy number variations eg VNTRs with multiple alleles
Statistical analysis
lod score = log10 odds loci are linked odds loci are unlinked
•lod scores are logarithms, so data from separate families can be pooled from different pedigrees by adding lod scores
•lod score ≥ 3.0 indicates likelihood of observing the given pedigrees if the two loci are not linked is less than 1 in 1000