[Campbell Biology P.987] Consider two individuals, both with a plasma LDL level of 160 mg/dL... | Practice Question

Consider two individuals, both with a plasma LDL level of 160 mg/dL. Individual X is from the study group inactivating PCSK9 mutation , and Individual Y is from the control group two functional copies of PCSK9 . Based on the information and histograms, which individual would likely have a higher underlying predisposition or risk factor for cardiovascular disease, assuming all other factors are equal, and why?

  • A: Individual X (study group), because despite having a mutation that typically lowers LDL, their level is still high, suggesting other significant underlying risk factors.
  • B: Individual Y (control group), because their high LDL level is likely due to the presence of two functional PCSK9 genes, indicating a direct genetic predisposition.
  • C: Both individuals have the same risk since their current LDL levels are identical.
  • D: It is impossible to predict their relative risk without more detailed genetic sequencing and lifestyle information for both individuals.

Explanation

The inactivating PCSK9 mutation typically lowers LDL levels. Individual X, despite having this 'protective' mutation, still has a high LDL level of 160 mg/dL. This suggests that their body has a strong underlying predisposition or other significant risk factors for high LDL, which are powerful enough to counteract the beneficial effect of the mutation. In contrast, Individual Y, from the control group, has a 160 mg/dL LDL level within the expected though higher range for individuals without the mutation. Therefore, Individual X's high LDL level, in the context of their genetic mutation, indicates a higher intrinsic risk.