Question

question 29

given the following phenotypic reactions, determine the most probable genotype:

anti-d anti-c anti-e anti-c anti-e
+ + 0 0 +

o rr
o r1r1
o r2r2
o r
\

Explanation:

Determine the phenotype from reactions

Using the Rh Blood Group System knowledge point

• Anti-D: \(+\) (D antigen is present)
• Anti-C: \(+\) (C antigen is present)
• Anti-E: \(0\) (E antigen is absent)
• Anti-c: \(0\) (c antigen is absent)
• Anti-e: \(+\) (e antigen is present)

The phenotype is \(D+, C+, E-, c-, e+\), which is written as \(DCe/DCe\) or simply \(DCe\).

Translate phenotype to Fisher-Race and Wiener

Using the Wiener Nomenclature knowledge point

• The haplotype containing \(D\), \(C\), and \(e\) is written as \(DCe\) in Fisher-Race nomenclature.
• In Wiener nomenclature, the \(DCe\) haplotype is designated as \(R^1\) (or \(R_1\)).
• Since the individual is negative for both \(E\) and \(c\), they must be homozygous for \(C\) and \(e\).
• Therefore, the genotype must be \(R^1R^1\) (or \(R_1R_1\)).

Evaluate the given options

Using the Rh Genotype Frequencies knowledge point

• \(r'r'\): Represents genotype \(dCe/dCe\). This is D-negative, which contradicts the Anti-D \(+\) reaction.
• \(R_1R_1\): Represents genotype \(DCe/DCe\). This matches the phenotype \(D+, C+, E-, c-, e+\) perfectly.
• \(R_2R_2\): Represents genotype \(DcE/DcE\). This would be positive for \(E\) and \(c\), and negative for \(C\), which contradicts the reactions.
• \(r''r''\): Represents genotype \(dcE/dcE\). This is D-negative and positive for \(E\) and \(c\), which contradicts the reactions.

Address the student's specific query

Using the Wiener Nomenclature and Rh Genotype Frequencies knowledge points

• The student asked why option A (\(r'r'\)) is incorrect.
• The prime symbol (\('\)) in Wiener nomenclature denotes the presence of the \(C\) antigen without \(D\) (i.e., \(dCe\)).
• A lowercase \(r\) indicates the absence of the \(D\) antigen (D-negative).
• Since the patient's red cells reacted positively with Anti-D (\(+\)), the patient is D-positive.
• Therefore, any genotype starting with lowercase \(r\) (such as \(r'r'\) or \(r''r''\)), which represents D-negative states, is incorrect.

Answer:

• (A) r'r'
• (B) R1R1 (Correct answer)
• (C) R2R2
• (D) r"r"