Which genotype corresponds to the Lewis phenotype Le(a+b-)?

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Multiple Choice

Which genotype corresponds to the Lewis phenotype Le(a+b-)?

Le(a+b-) means Lea is present on red cells while Leb is not. Lea is produced by the Lewis gene FUT3 when its enzyme is functional, whereas Leb requires an active secretor enzyme FUT2 to add the second fucose to Lea to form Leb. If the Lewis gene is functional (Le) but the secretor gene is nonfunctional (nonsecretor), Leb cannot be formed, so Lea appears without Leb. The H antigen status (whether H is present or not) does not determine Lea formation; it mainly affects Leb formation only when secretor activity is present. So the genotype that yields Le(a+b-) is one with a functional Lewis gene (Le) and nonsecretor status, allowing Lea to be expressed but preventing Leb.

Le(a+b-) means Lea is present on red cells while Leb is not. Lea is produced by the Lewis gene FUT3 when its enzyme is functional, whereas Leb requires an active secretor enzyme FUT2 to add the second fucose to Lea to form Leb. If the Lewis gene is functional (Le) but the secretor gene is nonfunctional (nonsecretor), Leb cannot be formed, so Lea appears without Leb. The H antigen status (whether H is present or not) does not determine Lea formation; it mainly affects Leb formation only when secretor activity is present. So the genotype that yields Le(a+b-) is one with a functional Lewis gene (Le) and nonsecretor status, allowing Lea to be expressed but preventing Leb.

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