Question

a person has inherited the following genes:

le/le, se/se

what will their lewis rbc phenotype be at adulthood?

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

Explanation:

Analyze the inherited Lewis genotype

Using the Lewis Blood Group and Lewis Antigen Biosynthesis knowledge points

• The individual has inherited the homozygous recessive genotype \(le/le\).
• The \(le\) gene is an inactive amorph that does not produce a functional fucosyltransferase enzyme (FUT3).
• Without a functional \(Le\) gene, no Lewis antigens (\(\text{Le}^\text{a}\) or \(\text{Le}^\text{b}\)) can be synthesized in secretions or adsorbed onto red blood cell membranes.

Determine the effect of the Secretor genotype

Using the Lewis Phenotypes knowledge point

• The individual has inherited the homozygous dominant secretor genotype \(Se/Se\).
• Although a functional secretor enzyme (FUT2) is present, it acts on type 1 precursor chains to form type 1 H substance, but cannot synthesize Lewis antigens without the active \(Le\) gene.
• Consequently, no Lewis antigens are present in secretions to be adsorbed onto the red blood cells.

Identify the final adult red blood cell phenotype

Using the Lewis Phenotypes knowledge point

• Since neither \(\text{Le}^\text{a}\) nor \(\text{Le}^\text{b}\) antigens are synthesized or present on the red blood cells, the phenotype is negative for both.
• Therefore, the adult red blood cell phenotype is \(\text{Le(a-b-)}\).

Answer:

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