Question

Expression of the A and B antigens on red blood cells is influenced by the FUT1 gene. This gene encodes fucosyl transferase, an enzyme that helps produce the H substance. Which of the following statements about the H substance is incorrect?
(A) Individuals that cannot produce the H substance appear to be type O even if they have functional A and/or iB alleles.
(B) Individuals that fail to produce the H substance are said to have the Bombay phenotype.
(C) Individuals that are heterozygous for the FUT1 gene cannot produce the H substance
(D) The H substance is a substrate for the enzymes produced by the n and β genes. These enzymes add the appropriate terminal sugar to the H substance producing the A and B antigens, respectively.

Answer 1

Answer: The correct answer is option C

Explanation:

Bombay phenotype refers to a rare genetic trait in which a person appears as blood group O even in presence of functional A, B, or AB alleles.

It is because of recessive mutation that occurs in other locus, that is, FUT1 gene. Normal gene produces H antigen or protein in the cell. This antigen is essential for the final expression of the ABO alleles.

If a person is homozygous recessive then he or she is not able to produce H antigen due to which the blood group appears as O.

However, if a person carries even a single functional copy of FUT1 gene, that is, heterozygous or homozygous then he or she can efficiently produce H antigen and then ABO alleles are expressed accordingly.

Thus, option C contains incorrect statement.