RNA interference

The mRNA transcribed from a gene is called the sense RNA.
In antisense technology, a piece of RNA (or a gene producing RNA) with a sequence complementary to a specific mRNA is introduced into the cell. This is the antisense RNA.
The antisense RNA pairs with the complementary sense mRNA to form double-stranded RNA.
This double-stranded RNA cannot be translated and is degraded, so the expression of that specific gene is stopped (the gene is silenced).
Examples: the Flavr Savr tomato, in which the production of the enzyme polygalacturonase is blocked to delay softening, and RNA interference used to protect tobacco plants against the nematode Meloidogyne incognita.
The other statements describe unrelated things; in particular RNA polymerase does not produce DNA, and somaclonal variation arises in tissue culture.
So antisense technology is when a piece of RNA that is complementary in sequence is used to stop the expression of a specific gene.