what does 35s cysteine and 32 p phospate have to do with the labeling of newly replicated viruses?

Question

In my teacher's lab, she has two different kinds of labels for viruses - where would I expect to find them in a newly replicated virus?
1. 35 s cysteine
2. 32 p phospate

Answer 1

this is the classic Hershey and Chase expt proving that DNA was responsible for transmitting genetic information -- not the protein.
Phosphate is a component of DNA.
Cysteine, an amino acid, is a component of protein.
When the viruses were labelled with 32p Phosphate, the radioactivity was incorporated into the DNA. After the virus infected the bacteria, the DNA entered the cell, leaving the phage coat outside (which contains the 35S cysteine.) See, how polite the phage is to leave his coat outside :-) Jokes aside, the newly replicated virus would contain a strand of DNA from the original virus (cf. the Meselson Stahl experiement) and would contain radioactive 32P phosphate. There!

Answer 2

Well, you just have too look at what part of the virus has the most of these labels. Cysteine is an amino acid, right? So the virus would have encorporated it into all of it's proteins, which, in a virus particle, would be the protein coat that surrounds it. Phosphate is ubiquitous in most cells, but since viruses don't have a lot of kinases, ATP, NADPH, etc. (they rely on their host for that stuff) the phosphate concentration would be highest in the DNA. The phosphate-ribose backbone will contain high amounts of that radioactivity.