level: 17.5 Codominance and multiple alleles
Questions and Answers List
level questions: 17.5 Codominance and multiple alleles
| Question | Answer |
|---|---|
| Mutiple alleles (+ codominance) the ABO blood system | - Controlled by tri-allelic gene - Can generate 6 pehnotypes - The alleles control the production of the antigens on the surface of the red blood cells - Two of the alleles are codominant to one another and both are dominant over the third - Allele IA produces antigen A - Allele IB produces antigen B - Allele IO produces no antigen |
| 6 phenotypes | - IAIA A - IBIB B - IAIB AB - IOIO O - IBIO B - IAIO A |
| Symbols for codominance alleles | - Both alleles expressed in the heterozygous both take a capital case letter - An index letter (small at the top) indentifies the allele - Therefore: normal haemoglobin alleles is Hb (small N) - Siclcle cell allele is Hb (small S) Hbn Hbs = resistence to malaria |