Final answer:
To identify start sites for all genes in a pham, scientists create a genomic library, label DNA and protein coats with radioactive isotopes, and use techniques like Southern blotting after electrophoresis to isolate and study the gene of interest.
Step-by-step explanation:
To look at all of the start sites for all phage genes in a pham, or phage family, the process generally involves creating a genomic library and using molecular biology techniques to isolate specific genes. After spreading the library on a bacterial lawn to form plaques, each potentially containing a gene of interest, scientists use radioactive labeling (such as using 32P for DNA and 35S for protein coats), restriction digestion, gel electrophoresis, and Southern blotting to identify and isolate the gene from a clone that could be up to 20 kbp long. The smallest DNA fragment containing the gene can then be subcloned into a suitable vector for further study.