Autosomal recessive (or X-linked)
Same phenotype (disease) caused by mutations in different genes
Different mutations (alleles) in the same gene causing the same disease
Clinical (phenotypic) heterogeneity
Different mutations in the same gene that lead to different diseases
Do diseases work in an all-or-nothing fashion?
No! Many diseases work on contiuums (ex. cystic fibrosis)
Dominance and recessiveness are properties of __________, not _______
Characters, not genes
If the product from a heterozygote is not enough to cross threshold, the mutation is.....
If the reverse is true, it's recessive!
Autosomal dominant Inheritance Criteria
- Most affected individuals will be heterozygous
- expressed every generation
- Recurrence risk of 50%
- Affected individuals usually have affected parents
Autosomal recessive inheritance
- Both parents of affected individuals to be carriers and asymptomatic
- May appear as sporadic
- Recurrence risk is 1 in 4
An organism is a compound heterozygote if it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be mutated but at different locations). Compound heterozygosity reflects the diversity of the mutation base for many autosomal recessive genetic disorders; mutations in most disease-causing genes have arisen many times.
ex. cystic fibrosis
After birth and not affected by autosomal recessive disease, what is the chance a brother or sister of an affected individual have of being a carrier?
Describe the chances of parents, grandparents, uncles, and cousins being carriers...
X-linked recessive inheritance
- Usually males affected (unless an affected male marries a carrier female, or extreme X-inactivation)
- All daughters of affected males are carriers
- Half the sons of carrier females are affected
- No male to male transmission
???? look up!
- Affected males have normal sons and affected daughters
- Twice as many affected females as males
- Most affected females will be heterozygous, so offspring will be affected
- Usually more sever/lethal in males
No/few known Y linked diseases
Only males would be affected
Trait appears to be inherited exclusively through females
All offspring of affected females will probably be affected
Highly mutatable compared to nuclear DNA
Disease will appear sporadic but will be familial in descendents of affected individuals but not in earlier generations
Mitochondria have high mutation rate
Estimate of 100-200 new bp changes in each person
Germline or somatic
Tissue has two or more cell lines of different genotype (derived from single zygote)
ex. lymphoma or leukemia
Individuals derived from cells of two different zygotes
Ex. recipient would be bone marrow transplant from donor
Or absordbing twin in utero