1. A group of scientists is working with a type of skin cancer (melanoma) cells
ID: 67259 • Letter: 1
Question
1. A group of scientists is working with a type of skin cancer (melanoma) cells that can be grown in culture. These cells divide without control and form overlapping cell layers (both properties that are typical of cancer cells). A student that was interested in identifying natural anti-cancer products from tea leaves added the three different purified molecules to the cancer cell cultures. Each molecule the student added has a different effect on cell cycle control machinery. For each, use your knowledge of cell cycle control to state i) whether the molecule would be expected to block cell division in the cancer cells and ii) why or why not.
1a. Tea leaf molecule 1: binds to the cyclin-dependent kinase and prevents cyclins from interacting with the cdk
1b. Tea leaf molecule 2: causes excessive amounts of DNA damage in cells
1c. Tea leaf molecule 3: causes increased transcription of cyclin D, which activates the G1/S phase transition
Explanation / Answer
1a. Tea leaf molecule 1: binds to the cyclin-dependent kinase and prevents cyclins from interacting with the cdk
(will block cell division)
As their name suggests, Cyclin-Dependent Protein Kinases are dependent on cyclins, another class of regulatory proteins. Cyclins bind to Cdks, activating the Cdks to phosphorylate other molecules. Cyclins are named such because they undergo a constant cycle of synthesis and degradation during cell division. When cyclins are synthesized, they act as an activating protein and bind to Cdks forming a cyclin-Cdk complex. This complex then acts as a signal to the cell to pass to the next cell cycle phase.
We can also say that teaf leaf molecule 1 acts like p21 which is a potent cyclin-dependent kinase inhibitor.
1b. Tea leaf molecule 2: causes excessive amounts of DNA damage in cells
(will not block cell division as cell will not be able to overcome extensive damage which results in apoptosis through accumulation of p53)
1c. Tea leaf molecule 3: causes increased transcription of cyclin D, which activates the G1/S phase transition
(will not affect cell division as cyclin D which is involved in regulating cell cycle progression)
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