Mutations are often linked to diseases or negative impacts but silent mutations can be extremely beneficial in creating genetic diversity among species in a population. Germ-line mutations are passed from the parent to the offspring.[1][additional citation(s) needed] Scientists have predicted that people have approximately 5 to 10 deadly mutations in their genomes but this is essentially harmless because there is usually only one copy of a particular bad gene so diseases are unlikely.[8] Silent mutations can also be produced by insertions or deletions, which cause a shift in the reading frame.[2]