Patterns of Inheritance Flashcards
What is Pleiotrophy?
A mutation that can produce multiple distinct phenotypes that may or may not appear in a particular individual
What is a kindred?
A group of human beings each of which is related, genetically or by marriage to ever other member of the group
What is the proband?
Family member who draws attention to a pedirgree
What is an index case?
the clinically affected family member through whom attention is first drawn to a pedigree of particular interest to human genetics
What is penetrance?
The probability that a gene will have any phenotypic expression at all
What is expressivity?
The severity of expression of the phenotype
What are the characteristics of Autosomal dominant inheritance?
- Multiple generations affected
- Males and females are affected in equal proportion
- Male to male is possible
- Each offspring of an affected parent has a 50% of being affected
Describe Polycystic Kidney disease.
- Autosomal dominant
- Renal cysts, progressive renal failure, extrarenal problems
- Late onset
What are the characteristics of Autosomal recessive inheritance?
- Males and females are equally likely to be affected
- Both parents must be carriers to have an affected child
- Recurrence risk is 25% for each offspring of carrier parents
- Certain diseases are more common to certain ehtnicities
- Inquire about consanguinity
Describe Tay-Sachs disease.
Autosomal recessive
Severe mental and physical deterioration and death by 2 or 3
Higher incidence in Ashkenazi Jews
Describe Phenylketonuria (PKU)
Autosomal recessive
Mental retardation, fair skin, eczema, epilepsy
Preventable if prompt dietary treatment
What is Consanguinity?
A genetic relationship where individuals have at least one common ancestor in the preceding few generations
What is an isonymous marriage?
Marriage between persons with the same surname
Not necessarily indicative of consanguinity
What are the characteristics of X-linked recessive inheritance?
- Incidence much higher in males
- All daughters of affected males will be carriers
- Sons of females have a 50/50 chance
Lyonization may make symptoms milder in X-linked recessive disorders. What are some exceptions to this?
- Turner Syndrome (XO)
- Extreme lyonization
- Patients carrying X:autosome translocations