BrdU (bromodeoxyuridine) is a thymidine analog that can be naturally incorporated into DNA (in place of thymidine) and detected by specific anti-BrdU antibodies. In an experiment to study the regeneration capabilities of Schmidtea mediterranea, you first fed the worms with BrdU-containing food for 30 minutes. After two hours, you fixed and incubated the worms with a fluorescently labeled anti-BrdU antibody, and observed its tissues with a fluorescence microscope. The result was that some nuclei are labeled with fluorescence while others are unlabeled. Would you expect to observe neoblasts mostly among cells that have (Y) or have not (N) been labeled with fluorescence? Are the neoblasts expected to be scattered throughout the body (S) or localized to a certain region (L)? If you fixed the worms after a week, instead of two hours, would you expect the number of nuclei with detectable fluorescence to increase (I), remain unchanged (U), or decrease (D) compared to these results? Write down your answer as a three-letter string, e.g. YSD.

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Quizplus · Accepted Answer

The pulse of BrdU leads to incorporation of the thymidine analog into the DNA of only those cells that were replicating their DNA (in S phase, prior to mitosis) around the time of the pulse. These are neoblasts and they should be scattered throughout the body to be able to regenerate all the different tissues. With time, the cells divide and differentiate and the BrdU is "diluted" and distributed into more cells, most of which are not neoblasts.

BrdU (Bromodeoxyuridine) Is a Thymidine Analog That Can Be Naturally