Question

A person with blood group A produces antibodies against B. A person with blood group B produces antibodies against A. A person with blood group AB produces no antibodies. How can you explain this?

a. A and B alleles are co-dominant. Therefore, both A and B carbohydrates are present on the cell.

b. A is incompletely dominant over B. Both A and B carbohydrates are present on the cell.

c. A and B alleles are co-dominant. Half the cells have only A, and other half have only B. A person with blood group A produces antibodies against B. A person with blood group B produces antibodies against A

Answer 1

c. it has to do with the antibodies and antigens, not carbohydrates. Also A B alleles are co-dominant so b is completely out.

Answer 2

A normal appearing couple is found to be heterozygous recessive for albinism. Both have the genotype Aa. The gene responsible for albinism is recessive to the normal pigment-producing gene. What are the chances of their children being albino?

Answer 3

Do a punnet square. If the couple is heterozygous then they are Aa. AaXAa gives 1/4 AA 2/4 Aa and 1/4 aa. there is a 1/4 chance that the child will have the genotype aa which causes the phenotype of albinism because it is homozygous recessive.

Answer 4

Hmm, for the first one I would go with B.

Co-dominance occurs when the phenotype is half way between the fully dominant and fully recessive phenotypes but has the same elements of neither. An example is pink snap dragons which occur when red and white snap dragons are crossed.

Incomplete dominance, on the other hand, occurs when all organisms express both the recessive phenotype and dominant phenotype at the same time, as in the AB blood group which has both A carbohydrates and B carbohydrates on the surfaces of red blood cells...

Answer 5

Agree with @biogirl on the second question, though. ;D