Most of the time, a mutation in a virus results in better ability to infect a host cell and more resistance to the host cell's defenses.
They create genetic variations.
A point mutation, in which one nitrogen base in a codon is substituted for another, may have no effect on an organism. This is true if the base substitution does not change the amino acid that the codon represents, or if the mutation occurs in a non-critical location in the protein so that the protein's structure is not changed significantly and the protein is still able to function.
Influenza is an RNA virus. Being that it is an RNA virus it has a high rate of mutation that goes unchecked. This high rate of mutation leads to different strains of the influenza virus
A deleterious mutation has a negative effect on the phenotype, and thus decreases the fitness of the organism. (A harmful mutation)
The mutation may be passed on to an offspring. Depending on the mutation, it may have no effect, or it could be lethal.
No one knows what effect a mutation may have. Most are not viable.
The location of the mutation within the genome, the type of mutation (e.g., missense, frameshift), and its effect on gene function or protein structure typically determine the magnitude of a mutation's effect. Additionally, the degree to which the mutation disrupts important cellular processes or regulatory mechanisms can also influence its impact.
Well a Silent Mutation does not affect anything so it isn't bad so its a good mutation.
If the point mutation does not change the protein to be translated in the 3-letter sequence, then it will have no effect on the gene's function.
substitution
The Melissa virus is a mass-mailing macro virus. It can effect email that is sent and infect the computer when the email is opened.
It's a double mutation that occurs on a colony of cells (bacteria for example) that claims to have resistance to two different antibiotics or viruses. This double mutation, however, strictly happens by first developing a mutation for the first antibiotic/virus and then has an independent mutation (nothing to do with the first mutation) for the other or second antibiotic/virus.