Question

2). Your friend is interning in a research lab at CERN in Switzerland. The lab they are working in is studying a family of mice named the Quarks. The family consists of parents named Up and Down, monozygotic twins Charm and Strange, and their third child Bottom. In other words, Bottom is Charm and Strange’s little brother (and all three mice are the offspring of Up and Down). At the immunoglobulin heavy chain locus Up is homozygous for g3^a and Down is heterozygous, having both g3^a and g3^b (note: in mice the different alleles are named with letter superscripts).

a). Charm has come down with a disease caused by Micrococcus blackholeus and she is unable to launch an effective antibody response against the bacteria. However, the rest of the Quarks have all encountered the pathogen and produced high levels of IgG antibodies against the bacteria. Your friend wants to transfer immunoglobulin to Charm from a family member to confer passive immunity.

            i. Which family member, if any, would be least likely to in induce anti-allotype antibodies in Charm? (1 point)

            ii. Which family member, if any, would be likely to induce anti-isotype antibodies in Charm? (1 point)

b). Would injecting serum IgG from Up into Down induce anti-allotypic antibodies? Why or why not? (1 point)

c). Bottom suffers from Higgs Syndrome, a condition characterized by extreme weight gain due to the presence of an anti-leptin IgG3 auto-antibody. Should your friend be able to guess which of the other family members will also develop this syndrome (i.e. have the same anti-leptin IgG3 antibody)? Explain your reasoning. (1 point)

d). Bottom has just discovered his long-lost evil twin Top. Top has a component in his serum called W particles. The W particles appear to be immunolglobulins and have been found to bind to IgG3 antibodies from Down. Using this information determine Top’s genotype for g3. (1 point)

Answer 1

a)

Ans i) The member who would be least likely in this is Down because of the immunoglobulin heavy chain locus is heterozygous.

Ans ii) The family member who can help induce anti-allotype antibodies in Charm is Up because he is homozygous for g3a which has higher probability of helping in the transmission and production.

Ans b) On injecting the serum IgG from Up to Down, it might not induce the formation of the anti-allotypic antidodies as Up is homozygous for it.

Ans c) The condition of Bottom i.e presence of anti-leptin IgG3 auto antibody might have been developed by Down. Being heterozygous it might be recessive but it got dominant in Bottom.