Question

question 45

a person has inherited the following genes:

le/le, se/se

what will their lewis rbc phenotype be at adulthood?

le(a-b+)
le(a+b-)
le(a+b+)
le(a-b-)

Explanation:

Analyze the inherited genotype

Using the Lewis Blood Group and Lewis Antigen Biosynthesis knowledge points
The individual has inherited the genotype \(le/le\) and \(Se/Se\). The \(le\) allele is an inactive, non-functional amorph of the FUT3 gene. Because the individual is homozygous recessive (\(le/le\)), they lack a functional fucosyltransferase enzyme required to synthesize Lewis antigens (\(\text{Le}^\text{a}\) or \(\text{Le}^\text{b}\)) from precursor substances.

Determine the resulting phenotype

Using the Lewis Phenotypes knowledge point
Without a functional FUT3 enzyme, no Lewis antigens can be synthesized or adsorbed onto the red blood cell membranes, regardless of the presence of the secretor gene (\(Se/Se\)). Therefore, the red blood cells will lack both \(\text{Le}^\text{a}\) and \(\text{Le}^\text{b}\) antigens, resulting in the \(\text{Le(a-b-)}\) phenotype at adulthood.

Answer:

• (A) Le(a-b+)
• (B) Le(a+b-)
• (C) Le(a+b+)
• (D) Le(a-b-) (Correct answer)