Question

which of the following is positive for g antigen?

• \\(rr\\)
• \\(rr\\)
• \\(rr\\)
• \\(rr\\)

Explanation:

Define the G antigen in the Rh system

Using the Rh Blood Group System knowledge point, the G antigen is a red blood cell antigen present on cells that possess either the D antigen or the C antigen. If a red blood cell has D, C, or both, it will test positive for the G antigen. It is absent only when both D and C are absent.

Translate Wiener nomenclature to Fisher-Race

Using the Wiener Nomenclature knowledge point:

• \(r\) represents \(cde\) (lacks D, C, E)
• \(r'\) represents \(Cde\) (possesses C, lacks D, E)
• \(r''\) represents \(cdE\) (possesses E, lacks D, C)

Evaluate each genotype for D and C antigens

We analyze the presence of D or C in each option:

• \(r''r\) corresponds to \(cdE/cde\). This genotype lacks both D and C antigens. Thus, it is G-negative.
• \(rr\) corresponds to \(cde/cde\). This genotype lacks both D and C antigens. Thus, it is G-negative.
• \(r'r'\) corresponds to \(Cde/Cde\). This genotype possesses the C antigen. Thus, it is G-positive.
• \(r''r''\) corresponds to \(cdE/cdE\). This genotype lacks both D and C antigens. Thus, it is G-negative.

Address the student's specific query

The student asked why option C (\(r'r'\)) is incorrect. In fact, \(r'r'\) possesses the C antigen (\(Cde/Cde\)), which makes it positive for the G antigen. Therefore, \(r'r'\) is the correct answer to the question "Which of the following is positive for G antigen?".

Answer:

• (A) \(r''r\)
• (B) \(rr\)
• (C) \(r'r'\) (Correct answer)
• (D) \(r''r''\)