A mutated form of a gene is called a mutant allele. When the new allele is created, a heterozygote containing the newly created allele as well as the original will express the new allele; genetically this defines the mutations as dominant phenotypes.
A back mutation or reversion is a point mutation that restores the original sequence and hence the original phenotype.
The concepts developed in this paper suggest new avenues for future experimentation, help to explain previously unclear observations, and recommend new methods to impede cancer development, including blocking the defined sequence that is required to produce a tumor.
Large scale changes to the structure of chromosomes called chromosomal rearrangement that can lead to a decrease of fitness but also to speciation in isolated, inbred populations. Are Mutations Random?
Another type of chromosome mutation is the gain or loss of whole chromosome sets. But mutations occur randomly over a lifetime.
At the intermediate level, indels can affect parts of a gene or whole groups of genes. One way to think of DNA and RNA is that they are substances that carry the long-term memory of the information required for an organism's reproduction.
Most are eliminated by chance. Small-scale mutations[ edit ] Small-scale mutations affect a gene in one or a few nucleotides. By effect on function[ edit ] Loss-of-function mutations, also called inactivating mutations, result in the gene product having less or no function being partially or wholly inactivated.