Problem1 Blood cell antigens are carbohydrates or proteins found on the surface

Question

Problem1 Blood cell antigens are carbohydrates or proteins found on the surface of red blood cells. The two most important types of antigens are the A and B antigens which determine if you have A, B, AB or O blood, and the Rh D antigen, which determines if you have positive or negative blood. A and B antigens are carbohydrate molecules. The ABO gene produces a protein enzyme that catalyzes the formation of A or B antigens. This gene has three alleles The IA allele produces a protein that catalyzes the production of A The I allele produces a protein that catalyzes the production of B The i allele does not produce a functioning protein, so neither A or B antigens antigens antigens are formed. The A and B alleles are dominant to the i allele and co-dominant to each other. The RhD gene produces D proteins that are embedded in the cell membrane and function as antigens. This gene has two alleles: .The D allele (dominant) produces D antigen proteins. A person with the DD or Dd genotype has the D antigen protein on their red blood cells, and therefore, is said to have Rh positive blood (they are positive for the D antigen). The d allele (recessive) produces no antigen proteins. A person with the dd genotype has no D antigens and is said to have Rh negative blood The drawing below shows the blood cell antigens that are present on blood cells from the 8 major blood types. B antigen-carbohydrate A antigen-carbohydrate Dantigen- Protein AB+ AB- 0 A man with AB-blood marries a woman with O+ blood. Their first child has B- blood. What are the possible genotypes and phenotypes for their second child, an b) what is the probability of this second child having each genotype and phenotype. Show your work!

Explanation / Answer

a) Parents genotype - IaIb  × ii

Gametes - Ia Ib   × i

F1 generation - Iai Ibi

Here IaIb represent AB blood group and ii represent O blood group

The child can either have A blood group or B blood group

Rh factor

Parents - dd × Dd

Gametes - d × D d

F1 generation - dd Dd   

So the second child can be A+,A-, B+ ,B-

b) The probability of getting

Iai or Ibi is -0.5 or 50%

and Dd or dd is - 0.5 or 50%

Phenotypic probability

For A+ - 1/2 *1/2

(i. e ) the probability of getting A blood group * probability of getting Rh factor to be positive

So the probability is 0.25 or 25%

Similarly the probability for A-, B+ ,B- is 0.25 or 25%

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