An Experiment Is Performed in Which a Point Mutation Is $\zeta$

question 10

Multiple Choice

An experiment is performed in which a point mutation is introduced randomly into the Zap-70 gene for a particular strain of mice.The mutant mice display a defect in T cell development.However,precursor T cells isolated from the thymus of these mice show normal expression levels of Zap-70 of the correct molecular weight.On further in vitro analysis,the mutant Zap-70 is found to bind to ITAM motifs in the cytoplasmic tail of the $\zeta$ chain,but only when the $\zeta$ chain is phosphorylated.No phosphorylated LAT is detected,however.Given these data,in which of the following protein domains is the mutation most likely to be present?

• A)Pleckstrin homology (PH)domain
• B)Proline-rich (PR)domain
• C)SH1 domain
• D)SH2 domain
• E)SH3 domain

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