Problem 10 - Biology: The Dynamic Science

Question

During embryonic development in many humans, the cells of the lower earlobe die resulting in an unattached earlobe. For this to occur one would deduce that: a. \(\quad C E D-3\) genes are inhibited. b. \(\quad C E D-4\) genes are inhibited. c. caspase-9 is deactivated. d. \(\quad C E D-9\) is actively expressed. e. the proteins encoded by \(B c l\) genes are inactivated.

Step-by-Step Solution

Answer

The correct answer is option d. During embryonic development in many humans, the lower earlobe's cells die when the \(C E D-9\) gene is actively expressed.

Step 1: Understanding the role of each gene

The \(C E D-3\) gene and caspase-9 are all effector caspases in the cell apoptosis process, which means their activation can induce cell death. The \(C E D-4\) gene, when activated, can activate these effector caspases. \(C E D-9\) and \(B c l\) genes, conversely, inhibit the apoptosis process when they're active. Inactivation of these genes implies that the apoptosis process will take place.

Step 2: Analyzing The Answer Options

Looking carefully at the options, we can eliminate options a, b, and c because the inhibition of the \(C E D-3\), \(C E D-4\) genes and deactivation of caspase-9 would not facilitate cell death but rather prevent it from happening. On the other hand, if the \(B c l\) genes' proteins were inactivated (option e), that would also lead to cell death. However, this option does not fit the scenario because if all the \(B c l\) genes' proteins were inactivated, not only the lower earlobe cells but most cells in the body will undergo apoptosis, which isn't what happens in typical human embryonic development.

Step 3: Deciding on the Correct Answer

The only logical deduction left is that the \(C E D-9\) gene is actively expressed (option d). This gene, when actively expressed, inhibits the apoptosis inhibitors from functioning and thus, allows the apoptosis process to occur in the cells of the lower earlobe in many humans during embryonic development.