Inheritance Patterns Flashcards
vertical transmission
phenotype seen in every generation
horizontal transmission
phenotype seen in siblings, but not parents
autosomal dominant
-affected offspring typically have one heterozygous parent
-vertical transmission
-equal bt male and female
-50% recurrence risk
examples of autosomal dominant diseases
-neurofibromatosis type 1
-marfan syndrome
-achondroplasia
-osteogenesis imperfecta
-breast and ovarian cancer
-postaxial polydactyly
multiple phenotypic effects of a single allele or pair of alleles
pleiotropy
-ex. marfan syndrome has ocular, skeletal, and cardiovascular effects
autosomal recessive
-parents are both heterozygous (carriers)
-horizontal transmission
-either parent can pass to son and daughter
-25% recurrence risk
examples of autosomal recessive inheritance
-sickle cell
-cystic fibrosis
-PKU
-tay-sachs
spinal muscle atrophy
x linked recessive
-vertical but skips generations
-more males than females affected
-carrier female (half sons affected/unaffected & half daughters carriers/noncarriers)
-affected male ( all daughters carry & all sons unaffected)
-non male to male
x linked recessive examples
hemophilia A & B
Duchenne muscular dystrophy
red green colorblind
-mutation in genes for clotting factor
-bleeding into soft tissues, muscles, and weight bearing joints
hemophilia
x linked dominant
-vertical transmission
-twice as many females affected
-affected females are heterozygous
-affected female (half daughters and sons affected/unaffected)
-affected male (all daughters affected, all sons unaffected)
-no male to male
example of x linked dominant
vitamin D-resistant rickets
y linked inhertiance
-vertical transmission
-all males
-only father to son
mitochondrial inhertiance
-vertical transmission
-equal male and female affected
-only passed from mom
reduced penetrance
-individuals with the genotype may not express the phenotype
-offspring still at risk
-example breast and ovarian cancer
age dependent penetrance
-symptoms of disease have delayed onset so they may have children before their symptoms show and the offspring are still at risk
variable expressivity
-severity of symptoms vary widely
-offspring still at risk
-individuals presentation may be so mild that they may not know they are affected until child is severely affected
with a new mutation, do siblings have an increased risk of disease?
no, ex achondroplasia
presence of genetically distinct cell lines in the same individual
mosaicism
mutation arises from mitotic errors after fertilization and propagates through multiple tissues or organs
somatic mosaicism
-two or more siblings affected with no family history
mutation only in egg or sperm cells
germline mosaicism
anticipation
-more severe expression and/or earlier age of onset in subsequent generations
-can be caused by expansion of DNA repeats
