Pedigrees Flashcards
1
Q
How can you recognize an autosomal recessive pedigree?
A
- Common for affected individuals to be born to unaffected parents.
- Affected individuals will include both males and females equally
- If the condition is rare most people do not carry an abnormal allele and those that do, carry it in the heterozygous form
- If both parents are affected, then all children are affected
- Not seen in every generation
2
Q
How can you recognize an autosomal dominant pedigree?
A
- Affected individuals WILL have an affected parent
- Males and females are affected equally
- Either sex transmits the allele
- If one parent is affected and another is not, the expected frequency is approximately 50/50 in offspring of affected and unaffected
- Two unaffected parents will never have affected children
- Two affected parents can have unaffected offspring. Often, dominant traits occur in the heterozygous condition as two dominant (mutant) alleles can be fatal. This is not the case for all diseases though.
3
Q
How do you recognize X-linked recessive traits in a pedigree?
A
- More males are affected that females
- If a female is affected, then all male offspring will be affected, and all females will be carriers assuming the father is normal
- If a male is affected, all daughters will be carriers and no sons will be affected
- If a male is unaffected, no female offspring will be affected
- There are no male carriers
4
Q
How do you recognize X-linked dominant traits in pedigrees?
A
- An affected female passes the trait to 50% of offspring
- An affected male passes the condition to 100% of daughters but never to sons
5
Q
How do you recognize Y-linked traits in pedigrees?
A
- 100% of the affected individuals are males
- If the father is affected, all sons are affected
6
Q
How do you recognize mitochondrial inherited traits in pedigrees?
A
The trait will pass through the maternal line and affect ALL children.
