assignment) A family of six (mother, father, and four children) had two children
ID: 208059 • Letter: A
Question
assignment) A family of six (mother, father, and four children) had two children with a history of chronic illness. Both children had repetitive infections of the sinuses, middle ears, and lungs due to a variety of respiratory viruses. Their other siblings were generally healthy and showed no signs of persistent or recurrent virus infections. The two affected children had normal numbers of B cells, T cells, and NK cells in their blood. They also showed no defects in neutrophil function or in complement protein levels. The two children also had normal antibody levels to vaccine protein antigens, such as tetanus toxoid, and had normal T cell responses to antigens from the vaccine strain of Mycobacterium tuberculosis after being vaccinated. Blood cells from one parent, one healthy child and the two affected children were examined for surface MHC protein expression by flow cytometry using two antibodies, one that recognizes all HLA class I proteins, and one that recognizes all HLA class II proteins. The results are shown in the figure below a) Analysis of HLA genotypes from the two affected children showed that they shared one haplotype of this locus. This haplotype encodes a common HLA-A allele, HLA-A2. Based on these data, is it likely that the two affected children have a point mutation (or mutations) in the coding sequence for HLA-A2? Why or why not? (3 points) -negate co ol artibody parent bealthy child atlected child atlected child b) Name two proteins that could be candidates for the defective gene in the two affected children. (2 points)Explanation / Answer
As provided in the graphs, the MHC (major hisptocompatibility complex) class I demonstrates a deviation from the curve as obtained in case of the parents and the other two children. The red and blue curves in the first graph of the MHC class I indicates the affected children.
The grey area in the graph is a the negative control antibody. the affected children do not demonstrate resistance. therefore, it can be concluded that there is a mutation in the MHC class I. The HLA (human leukocyte antigen)-A is a type of MHC class I molecule. So, it can be said that there is a mutation or a point mutation in the HLA-A2.
b.
The ubiquinated cytosolic proteins and the peptides are the proteins that may be affected by the mutation because these are responsible for the expression of intracellular proteins that are triggered by the T-cells for the destruction.
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