SSCE VCE Biology Immunity and Disease Response: Many gene loci are involved in d

Question

Many gene loci are involved in determining blood groups. One gene, the ABO gene, is responsible for the ABO blood groups. This gene locus has the alleles  
I^A : A antigen produced  
I^B : B antigen produced  
i : no antigen produced

There are four phenotypes, called blood groups, in this system. They are A, B, AB and O.  
a. Complete the following table using the allele symbols given above.

Blood group  
Possible genotypes  
B  
AB

Another gene associated with blood groups has the alleles H (H substance) and h (lack of H substance). The pathway involved can be summarised as follows.

mucopolysaccharide precursor  
in the presence of at least one H allele  
→ H substance

b. Write the genotype of an individual who fails to produce H substance.

H substance is the substrate for the production of the antigens associated with the ABO blood group. For example

H substance in presence of I^A allele  
→ A antigen is produced

c. To which blood group would a person with the genotype hh I^B be assigned after routine blood-group testing?

H substance is also called H antigen. The H antigen and antigens of the ABO blood-group system are found in some body fluids, for example in saliva.  
d. Complete the following table.

Genotype  
Antigens appearing in saliva  
Hh I^A  
HH ii

Many gene loci are involved in determining blood groups - VCE - SSCE Biology - Question 3 - 2008 - Paper 1

Worked Solution & Example Answer:Many gene loci are involved in determining blood groups - VCE - SSCE Biology - Question 3 - 2008 - Paper 1

a. Complete the following table using the allele symbols given above.

b. Write the genotype of an individual who fails to produce H substance.

c. To which blood group would a person with the genotype hh I^B be assigned after routine blood-group testing?

d. Complete the following table.

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