Suppose D were dominant and d were recessive, and you could…

Suppоse D were dоminаnt аnd d were recessive, аnd yоu could label the D allele in the P generation with a radioactive tag that could be detected in offspring (similar to how the Hershey-Chase experiment radiolabeled DNA and protein in bacteriophage). You create F1 hybrids by mating your radioactive DD individuals to dd individuals. Next, you cross two F1 individuals and produce 1000 F2 offspring. Among the F2 individuals, how many would you predict would have the radioactive label?