The meaning of "in which case"

In the below paragraph,

Either the viral genetic material can take over the cell's activity to make it produce many new viral particles, called virions, or it can become part of the host cell's genes, in which case it will be duplicated along with the genes, so that when the cell divides, both new cells will carry the viral genes.

? in which case; in the case of it becoming part of the host cell's genes

? in which case; either in the case of the viral genetic material can take over the cell's activity or it can become part of the host cell's genes

I'm not sure whether which one between ? & ? 'in which case' represent.