Question

an adult males rbc phenotype is le(a+b-). what genes has this person likely inherited?

le/le, se/se
le/le, se/-
le/-, se/se
le/-, se/-

Explanation:

Analyze the given phenotype

Using the Lewis Phenotypes knowledge point
The adult male's red blood cell (RBC) phenotype is \(Le(a+b-)\). This means his RBCs express the \(Le^a\) antigen but do not express the \(Le^b\) antigen.

Determine the Lewis gene status

Using the Lewis Antigen Biosynthesis knowledge point
To express any Lewis system antigens on RBCs, an individual must inherit at least one functional \(Le\) allele (genotype \(Le/Le\) or \(Le/le\), represented as \(Le/-\)). If they were homozygous recessive (\(le/le\)), they would have the \(Le(a-b-)\) phenotype. Therefore, this person must have inherited the \(Le\) gene:

$$ \text{Lewis Genotype: } Le/- $$

Determine the Secretor gene status

Using the Lewis Antigen Biosynthesis knowledge point
The \(Le^a\) antigen is converted into the \(Le^b\) antigen by the action of the fucosyltransferase encoded by the Secretor (\(Se\)) gene.

• If a person has the \(Se\) gene (\(Se/-\)), \(Le^a\) is converted to \(Le^b\), resulting in the \(Le(a-b+)\) phenotype.
• If a person is a non-secretor (\(se/se\)), the \(Le^a\) antigen cannot be converted to \(Le^b\). Thus, only \(Le^a\) remains on the RBCs, resulting in the \(Le(a+b-)\) phenotype.

Therefore, this person must be a non-secretor:

$$ \text{Secretor Genotype: } se/se $$

Combine the inherited genotypes

Using the Lewis Antigen Biosynthesis and Lewis Phenotypes knowledge points
Combining the requirements for the \(Le(a+b-)\) phenotype:

• Must have inherited the \(Le\) gene: \(Le/-\)
• Must be a non-secretor: \(se/se\)

This corresponds to the genotype combination:

$$ Le/-, se/se $$

Answer:

• le/le, se/se
• le/le, Se/-
• Le/-, se/se (Correct answer)
• Le/-, Se/-