Question

what is gene of and on ?
what does it mean ?

Answer 1

When a gene is "off" it means that gene's product (usually a protein) is not being created in the cell. When a gene is "on" it's just the reverse; the gene's product is being created in the cell. For example, humans produce lactase (a protein) to digest lactose (a sugar in milk) as infants; the lactase gene is "on". Humans that are lactose intolerant, however, have the lactase gene turned off as they leave infancy, so they can't digest lactose.