4. A research scientist studying the metabolic pathways that contribute to obesity feeds experimental animals a highcarbohydrate, high-protein diet for a prolonged period. A sample of liver tissue is then obtained from the animals, and the activity of various enzymes involved in fatty acid metabolism is measured and recorded. It is determined that beta-oxidation of fatty acids is inhibited within these cells as a result of the diet. An increase in which of the following substances is most likely responsible for the observed effect?
A. Acetoacetate
B. Camitine
C. Citrate
D. Malonyl-CoA
E. NADPH
5. A 6-year-old girl with chronic anemia requiring repeated blood transfusions is undergoing genetic testing. The patient’s mother and older sibling have a history of mild anemia. Her peripheral blood smear shows hypochromic, microcytic red blood cells, and hemoglobin electrophoresis reveals a predominance of hemoglobins F and A2. Sequencing of the β-globin gene is performed using the patient’s erythroblast DNA. A schematic representation of the gene and its transcribed RNA is shown in the image below.
The base sequence indicated by the bold red arrow is responsible for which of the following functions?
A. Enhancement of transcription
B. Initiation of transcription
C. Initiation of translation
D. Repression of transcription
E. Termination of transcription
6. A 2-year-old boy is evaluated for easy bruising. His parents report that he develops marked bruising and open wounds following minor trauma. The skin is difficult to suture due to its extreme fragility. Physical examination reveals hyperextensible skin, multiple ecchymoses over the forearms and pretibial regions, and an umbilical hernia. A skin biopsy is performed, and histochemical evaluation of the biopsy reveals a defect in extracellular processing of collagen. Which of the following steps of collagen synthesis is most likely impaired in this patient?
A. Glycosylation of hydroxylysine residues
B. lnterchain C-terminal disulfide bond formation
C. N-terminal propeptide removal
D. Proline residue hydroxylation
E. Triple helix formation