Ineed to know the answe for the first an second?

The rat has both alleles.
It manifests black fur - black fur dominant!
White fur recessive.

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.