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Free notes, MCQs, tables & flowcharts for USMLE Step 3 Biochemistry
A 4-year-old boy with beta thalassemia requires regular blood transfusions a few times per month because of persistent anemia. He is scheduled for a splenectomy in the next several months. Samples obtained from the boy’s red blood cells show a malformed protein with a length of 160 amino acids (in normal, healthy red blood cells, the functional protein has a length of 146 amino acids). Which of the following best accounts for these findings?
ANonsense mutation
BSilent mutation
CMissense mutation
DSplice site mutation
EFrameshift mutation
A group of scientists is studying the molecular mechanisms of protein synthesis. In the picture is the theoretical structure for tRNA. Where is the binding site for an amino acid?
AA
BB
CC
DE
ED
A 20-year-old female presents to the emergency department with squeezing right upper quadrant pain worse after eating. She has a history of a microcytic, hypochromic anemia with target cells. Physical exam shows severe tenderness to palpation in the right upper quadrant and a positive Murphy's sign. By genetic analysis a single point mutation is detected in the gene of interest. Despite this seemingly minor mutation, the protein encoded by this gene is found to be missing a group of 5 consecutive amino acids though the amino acids on either side of this sequence are preserved. This point mutation is most likely located in which of the following regions of the affected gene?
AIntron
BExon
CKozak consensus sequence
DTranscriptional promoter
EPolyadenylation sequence
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