Please answer all parts. Thank you. In typical human fibroblasts in culture, the

Question

Please answer all parts. Thank you.

In typical human fibroblasts in culture, the G1 period of cell cycle lasts about 10 hours, S lasts about 9 hours, G2 takes 4 hours, and M takes 1 hour. Assume the cells to be completely asynchronous (all are not in the same period of cell cycle, but in the different stages), and assume that the cells are evenly distributed in time. 1. minutes, and then washed it out and replaced it with an ordinary medium. What percentage of cells would you expect to become labeled by incorporating the 3H-thymidine into their DNA? a. How long would you have to wait after removing the 3H-thymidine medium before you would see labeled metaphase chromosomes? b. c. Would one or both chromatids be labeled?

Explanation / Answer

Answer a) since it is a radioactive isotope, and placed in the medium for 5 minutes, so it may be possible that 70-80% cells have been affected by this.

Answer 2) It may take hardly 7-8 hours to reach at M-phase after exposure of thymidine.

Answer 3) since thymidine stains nucleus, so chromosomes will also get stained, hence 2 chromatids will also be stained in the nucleus.

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