Introduction to the Pedigree Flashcards
Dominant pedigree vs. Recessive pedigree
- If two affected people have an unaffected child, it must be a dominant pedigree: D is the dominant mutant allele and d is the recessive wild type allele. Both parents are Dd and the normal child is dd.
- If two unaffected people have an affected child, it is a recessive pedigree: R is the dominant wild type allele and r is the recessive mutant allele. Both parents are Rr and the affected child is rr.
- If every affected person has an affected parent it is a dominant pedigree.
Assigning genotypes for a dominant pedigree: 1. All unaffected are ___
dd
Assigning genotypes for a dominant pedigree: 2. Affected children of an affected parent and an unaffected parent must be ________, because________
heterozygous Dd
they inherited a d allele from the unaffected parent
Assigning genotypes for a dominant pedigree: 3. The affected parents of an unaffected child must be ________, since ________
heterozygotes Dd
they both passed a d allele to their child.
Assigning genotypes for a dominant pedigree: 4. Outsider rule for dominant autosomal pedigrees: An affected outsider (a person with no known parents) is assumed to be ________
heterozygous (Dd).
Assigning genotypes for a dominant pedigree: 5. If both parents are heterozygous Dd x Dd, their affected offspring have a ________ chance of being Dd and a ________ chance of being DD.
2/3
1/3
Assigning genotypes for a recessive pedigree: 1. All affected are ________.
rr
Assigning genotypes for a recessive pedigree: 2. If an affected person (rr) mates with an unaffected person, any unaffected offspring must be ________, because ________
Rr heterozygotes
they got a r allele from their affected parent
Assigning genotypes for a recessive pedigree: 3. If two unaffected mate and have an affected child, both parents must be ________.
Rr heterozygotes
Assigning genotypes for a recessive pedigree: 4. Recessive outsider rule: outsiders are those whose parents are unknown. In a recessive autosomal pedigree, unaffected outsiders are assumed to be ________, ________.
RR, homozygous normal
Assigning genotypes for a recessive pedigree: 5. Children of RR x Rr have a ________ chance of being RR and a ________ chance of being Rr. Note that any siblings who have an rr child must be ________.
1/2
1/2
Rr
Assigning genotypes for a recessive pedigree: 6. Unaffected children of Rr x Rr have a ________ chance of being Rr and a ________ chance of being RR.
2/3
1/3
Y-linked Pedigrees: ________ will be affected, and must have ________.
ONLY MALES
an affected father
Sex-Linked Dominant
o One half the offspring on an afflicted heterozygote female will be affected (gender independent)
o Only the female progeny of afflicted males will be affected, since males donate their Y chromosome to sons
Sex-Linked Recessive
o Example: red-green colorblindness
o Likelihood that a woman will carry the allele is much higher than the likelihood that the women will display the phenotype associated with that allele. Half of their sons, however, will receive an X chromosome carrying that recessive allele.
o Likelihood that a male will display the associated trait is equal to the frequency of the allele in the general population while the probability that any given female will carry it is equal to frequency of the allele squared.
