Mutations: Types, Mechanisms, Mutagens and Ames test
- Any inheritable physical change in the DNA sequence of an organism is a mutation.
- Mutations are the source of the altered versions of genes that provide the raw material for evolution.
- Most point mutations have no effect on the organism, especially among the eukaryotes, because a large portion of the DNA is not in genes and thus does not affect the organism’s phenotype.
- Of the mutations that do affect the phenotype, the most common effect of mutations is lethality, because most genes are necessary for life.
- Only a small percentage of mutations causes a visible but non-lethal change in the phenotype.
Types of mutations (types of cells)
- Occur in all the cells of the body, excluding the germline
- Affects subsequent somatic cell descendants
- Not transmitted to offspring
- Mostly resulted in tumor or cancer
Germ line Mutation
- Mutations that occur in the germline cells
- Possibility of transmission to offspring
- Inheritable genetic disorders
Types of Mutation (Sources)
Mutation that occur without the known cause. It may occur due to:
- Inaccuracy in replication by DNA replication machinery
- Inefficiency of the DNA repair mechanisms for the repair of damaged DNA
- Degree of exposure to unknown mutagenic agents in the environment
Mutations are induced by exposure to physical (radiation; UV or ionizing radiation) or chemical mutagens.
- Hermann J. Muller and Edgar Alternburg measured the frequency of X-linked recessive lethal mutations in Drosophila.
- Muller demonstrated that exposing Drosophila sperm to X-rays increased the mutation frequency