Are all mutations deadly?

Though it's a common misconception that mutations are "bad," in reality, they differ greatly from one another. Some mutations have even been shown to be beneficial during the course of evolution.

The most well-known example of advantageous mutations is found in the following Wikipedia entry: [quote] Another example is sickle-cell disease, a blood disorder in which the body produces an abnormal type of hemoglobin in red blood cells, which carries oxygen. One-third of all indigenous inhabitants of Sub-Saharan Africa carry the gene because, in areas where malaria is common, carrying only one sickle-cell gene (sickle cell trait) is advantageous for survival because those who carry only one of the two sickle-cell disease alleles are more resistant to malaria because the sickling of the cells that the parasite infects prevents the malaria parasite.

The mutation that causes cancer is the most prevalent example of a bad mutation.

No, not all mutations are deadly. Mutations can range from harmless to beneficial to harmful, depending on various factors such as their location in the genome and the specific change they cause in the genetic code.