Single gene inheritance Flashcards
What is a proband and its other names?
Refers to the affected member that first brought it to the attention of physician/genetic consultant
Propositus or index case
What are the basic aspects of Mendelian princliple?
Existence of two genes responsible for character
May be homozygous or heterozygous
What are the five types of single gene disorders?
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
Mitochondrial
What are characteristics of autosomal dominant disorder inheritance?
Expressed in both heterozygous and homozygous conditions
May be more severe in homozygotes
Generally an affected person has an affected parent
Male and females equally
Affected persons in every generation
What is penetrance?
Describe the probability with which a carrier of dominant mutation will show signs - should be 100%
All or none measure
What is incomplete penetrance?
When gene fails to be expressed
What are characteristics of autosomal recessive disorder inheritance?
Only expressed in homozygotes
Heterozygotes are asymptomatic carriers
Males and females equally affected
Most receive gene from both parents
Consanguinity of parents is a strong cause for occurrence
What are characteristics of X-linked inheritance?
Males are mostly hemizygous
Female parent to both male and female offspring
Male parent to only female offspring
What are characteristics of X-linked recessive disorder inheritance?
Mostly expressed in males
Affected males daughters are all carriers
Sons inherit from mothers only
Can skip generations
Females may be manifesting heterozygotes and have symptoms with variable severity
What are characteristics of X-linked dominant disorder inheritance?
Seen in males and females
Generally visible in all generations
Affected males have normal sons and all affected daughters
Less common
What are examples of autosomal dominant conditions?
Familial hypercholesterolemia
Neurofibromatosis type I
Marfan syndrome
Achondroplasia
Osteogenesis imperfecta
Acute intermittent porphyria
Porphyria cutanea tarda
Polycystic kidney disease
What are examples of autosomal recessive?
Cystic fibrosis
Phenylketonuria
Tay-Sach disease
Sickle cell anemia
Hemochromatosis
Von Gierke disease
Xeroderma pigmentosum
What are examples of X-linked recessive diseases?
Duchenne muscular dystrophy
Hemophilia A and B
Glucose 6-phosphate dehydrogenase deficiency
Ornithine transcarbamyolase deficiency
Hunter disease
Fabry disease
Lesch Nyhan syndrome
Sideroblastic anemia
What are examples of X-linked dominant disorders?
Ret syndrome
Vit D resistant rickets
Pyruvate dehydrogenase deficiency
What are characteristics of mitochondrial disorders?
Maternal inheritance - nothing from father
May occur by sporadic somatic mutation by large deletion - not inherited
