Pedigree analysis Flashcards
Provide an example of disorder for each mode of inheritance
Autosomal dominant : Huntington’s disease
Autosomal recessive: albinism
X-linked dominant: Fragile X syndrome
X-linked recesssive: red-green color blindness, hemophilia
Y-linked : webbed toes
What is a pedigree ?
Diagram based on phenotypes that represents the ancestral relationships and transmission of genetics traits over several generatinos in a family
True or false : Pedigree’s are useful only if a trait follows Mendelian laws
true
What’s a proband ?
Individual whose penotype first brought attention to the family about
Define hemizygous
individual with only one copy of a particular gene (human males have one X –> they are heterogametic)
Describe a pedigree representing the autosomal recessive mode of inheritance
- Affected people are usually born to unaffected parents
- Parents of affected people are heterozygous (asymptomatic carriers)
- Cannot be sex-linked (affects both males and females)
- May skip a generation
Describe a pedigree representing the autosomal dominant mode of inheritance
- An affected person usually has at least one affected parent
- Appears in every generation
- Affects either sex
- Transmitted by either sex
- A child of an affected x unaffected union has 50% chance of being affected
Describe a pedigree representing the X-linked dominant mode of inheritance
- Affects either sex, but more females than males
- Females are often more mildly and more variably affected than males
- The child of an affected female, regardless of its sex, has a 50% chance of being affected
- For an affected male, all his daughters but none of his sons are affected
How do we call the homologous parts of the sex chromosomes ?
PAR1 and PAR2
(pseudo-autosomal regions)
Describe a pedigree representing the X-linked recessive mode of inheritance
- Affects mainly males
- Affected males are usually born to unaffected parents ; the mother is normally asymptomatic carrier and may have affected male relatives
- Females may be affected if the father is affected and the mother is a carrier
- There is no male-to-male transmission in the pedigree
Describe a pedigree representing the Y-linked inheritance mode of inheritance
- Affects only males
- Affected males always have an affected father
- All sons of an affected man are affected
Describe consanguinity
When individuals are related by a common ancestor with the previous few generations
Complete : consanguinity increases the risk of expressing ___ disorders
Recessive genetic
