Mutations - Review
...are recognized because the phenotype of the organism has changed. Thus a mutation is a change of the DNA sequence within a gene or chromosome of an organism resulting in the creation of a new character or trait not found in the parental type. Mutations are changes to the nucleotide sequence of the genetic material of an organism.
Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens.
In multicellular organisms, mutations can be subdivided into two types
• Germ line mutations, which can be passed on to descendants. If a gene is altered in a germ cell, the mutation is termed a germinal mutation. Because germ cells give rise to gametes, some gamete s will carry the mutation and it will be passed on to the next generation when the individual successfully mates.
• Somatic mutations, which are not transmitted to descendants in animals. Somatic cells give rise to all non-germline tissues. Mutations in somatic cells are called somatic mutations. Because they do not occur in cells that give rise to gametes, the mutation is not passed along to the next generation by sexual means.
Cancer tumors are a unique class of somatic mutations. The tumor arises when a gene involved in cell division, a protooncogene, is mutated. All of the daughter cells contain this mutation. The phenotype of all cells containing the mutation is un controlled cell division. This results in a tumor that is a collection of undifferentiated cells called tumor cells.
Plants sometimes can transmit somatic mutations to their descendants asexually or sexually (in cases where flower buds develop in somatically mutated parts of plants).
A new mutation that was not inherited from either parent is called a de novo mutation.
Mutations create variation within the gene pool. Less favorable (or...
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