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Scientists investigated the role of a protein called CENP-W in mitosis - AQA - A-Level Biology - Question 5 - 2018 - Paper 3
Question 5
Scientists investigated the role of a protein called CENP-W in mitosis. Their method involved cell fractionation and ultracentrifugation. The scientists began by ly... show full transcript
Worked Solution & Example Answer:Scientists investigated the role of a protein called CENP-W in mitosis - AQA - A-Level Biology - Question 5 - 2018 - Paper 3
Step 1
Suggest how the detergent releases CENP-W from cells.
Answer
Detergents, being amphipathic molecules, interact with cell membranes made of phospholipids. When added to the cells, the detergent dissolves these lipids, leading to the breakdown of the cell membrane structure. This process disrupts the integrity of the cell, allowing CENP-W, which is generally bound within the cellular structures, to be released into the surrounding solution.
Step 2
Explain how ultracentrifugation separates CENP-W from other molecules.
Answer
Ultracentrifugation works by spinning the lysate at very high speeds, creating a strong centrifugal force. This force causes the molecules within the suspension to separate based on their mass, size, and density. Heavier and denser molecules, such as organelles, move towards the bottom, while lighter molecules, including CENP-W, may remain in the supernatant or form distinct bands. As such, it enables the separation of CENP-W from other cellular components.
Step 3
Suggest how the siRNA produced these results.
Answer
The siRNA binds to and degrades the mRNA for CENP-W, effectively preventing its translation into the protein. By inhibiting the synthesis of CENP-W, there is a significant reduction in its presence in the cells over time. After 48 hours, a noticeable decrease in the amount of CENP-W is likely visible in the gel electrophoresis results, whereas tubulin levels might not change as it is not affected by siRNA targeting CENP-W.