Please help, Genetics: Q1) In a maternity ward, four babies become accidentally
ID: 56178 • Letter: P
Question
Please help,
Genetics:
Q1) In a maternity ward, four babies become accidentally mixed up. The ABO types of the four babies are known to be O, A, B, and AB. The ABO types of the four sets of parents are determined. Indicate which baby belongs to each set of parents: (a) AB × O, (b) A × O, (c) A × AB, (d) O × O.
Q2) The following pedigree is for a dominant phenotype governed by an autosomal allele. What does this pedigree suggest about the phenotype, and what can you deduce about the genotype of individual A?
Explanation / Answer
(1)-
(a) ..........Parents AB ......................X...............O
Gametes- .....IA,IB...........................................Io
Progeny...........IAIo (Blood group A)..............IBIo (Blood group B)
(b)..............Parents A ......................X...............O
Gametes- .....IA, Io/ IA, IA...........................................Io
Progeny...........IAIo (Blood group A)..............IoIo Blood group O)..../ or exclusively IAIo (blood group A)
(c).....Parents AB ......................X...............A
Gametes- .....IA,IB...........................................IA/ IA , Io
Progeny.......IAIA (Blood group A).......IAIB (Blood group AB)/..or IAIA (blood group A), IAIo (A), IBIo (B), IAIB (AB)
(d) ....Parents O ......................X...............O
Gametes- .....Io...........................................Io
Progeny...........IoIo (Blood group O)
Hence for the parents set (d), the baby is exclusively of Blood group O- hence O belongs to (d).
AB blood group of the baby is only possible here for case (c); hence AB belongs to (c).
B blood group of the baby is not feasible for parent set (b)- hence Baby with blood group A belongs to (b).
Hence, A - (b); B - (a); AB- (c); O- (d).
2. Let the autosomal allele responsible for the trait be A. A is dominant over a.
The first genertaion: the mother is Aa & father is aa.
The second generation: first daughter is Aa, first son is aa, second son is Aa; second daughter - (?)
The third generation: both are Aa. So mother should be Aa; since father is aa (phenotypically normal).
Hence genotype of A is Aa; this pedigree indicates autosomal dominant inheritance.