Reference no: EM132666617
Study Guide
1.Tatiana Islayev was 17 years old when first seen at the Children's Hospital. She had severe bronchiectasis (dilation of the bronchi from repeated infections) and a persistent cough that produced yellow-green sputum. She had been chronically ill from the age of 4, when she started to get repeated infections of the sinuses, middle ears, and lungs apparently due to a variety of respiratory viruses. These often led to secondary bacterial infections and she had been prescribed frequent antibiotic treatment to control her persistent fevers and cough. Her brother Alexander, aged 7 years old, also suffered from chronic respiratory infections.
When Tatiana and Alexander were examined, they both had normal to somewhat elevated levels of IgG. When their white blood cells were typed for HLA antigens, no MHC class I molecules could be found on their cells. They expressed MHC class II molecules normally.
When cells from these siblings were grown in tissue culture, they were found to produce normal levels of mRNA for MHC class I molecules. When the DNA sequence of their TAP genes was determined, both Tatiana and Alexander were found to have a nonsense mutation in this gene.
a) Explain the relationship between the genetic defect present in these siblings and their susceptibility to the infections they experienced.
b) Why did Tatiana and Alexander have normal levels of serum IgG?
c) What is the relationship between TAP and proteasomes?
2) You are hired to work in a research laboratory that is studying the structure of antibody molecules. Your first on-the-job task is to do some reading about antibodies to learn about the genes encoding them. Your research supervisor asks that given your knowledge of the general arrangement of gene segments for the heavy chain proteins on chromosome 14 in humans that you:
a) Describe the gene segments rearrangements that must occur in the DNA to generate a region of DNA carrying the information for the variable region of a heavy chair.
b) Explain what happens during B cell maturation such that naïve B cells emerging from the bone marrow express both IgM and IgD on their surfaces.