Cyclin B1, a Key Cell Cycle Regulatory Protein in Vertebrates

question 20

Multiple Choice

Cyclin B1, a key cell cycle regulatory protein in vertebrates, is mostly cytosolic before mitosis. Early in mitosis, however, the protein is phosphorylated by certain protein kinases and consequently accumulates in the nucleus. How can phosphorylation bring about nuclear accumulation of this protein?

• A) Phosphorylation within the nuclear localization signal inhibits the function of the signal.
• B) Phosphorylation within the nuclear export signal enhances the function of the signal.
• C) Phosphorylation within the nuclear export signal interferes with the function of the signal.
• D) Phosphorylation elsewhere on the protein enhances binding to cytosolic proteins.

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Definitions:

Fixed Manufacturing Overhead

Costs incurred during the production process that do not vary with the level of production, such as rent for factory buildings, salaries of plant managers, and depreciation of manufacturing equipment.

Budget Variance

The variance between what was expected to be spent or earned, according to the budget, and the real amount that was spent or received.

Predetermined Overhead Rate

A rate used to allocate manufacturing overhead to individual products or job orders, based on a specific activity base, such as labor hours or machine hours.

Fixed Component

The portion of total costs that remains unchanged regardless of the level of production or business activity.