Wednesday, September 8, 2010

Mutations

In biology, 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, or viruses, or can occur deliberately under cellular control during processes such as hypermutation. In multicellular organisms, mutations can be subdivided into germ line mutations, which can be passed on to descendants, and somatic mutations, which are not transmitted to descendants in animals. Plants sometimes can transmit somatic mutations to their descendants asexually or sexually (in case when flower buds develop in somatically mutated part of plant). A new mutation that was not inherited from either parent is called a de novo mutation. The source of the mutation is unrelated to the consequence, although the consequences are related to which cells are affected.

Mutations create variations in the gene pool. Less favorable (or deleterious) mutations can be reduced in frequency in the gene pool by natural selection, while more favorable (beneficial or advantageous) mutations may accumulate and result in adaptive evolutionary changes. For example, a butterfly may produce offspring with new mutations. The majority of these mutations will have no effect; but one might change the color of one of the butterfly's offspring, making it harder (or easier) for predators to see. If this color change is advantageous, the chance of this butterfly surviving and producing its own offspring are a little better, and over time the number of butterflies with this mutation may form a larger percentage of the population.

Neutral mutations are defined as mutations whose effects do not influence the fitness of an individual. These can accumulate over time due to genetic drift. It is believed that the overwhelming majority of mutations have no significant effect on an organism's fitness. Also, DNA repair mechanisms are able to mend most changes before they become permanent mutations, and many organisms have mechanisms for eliminating otherwise permanently mutated somatic cells.

Ionizing radiation

Ionizing radiation refers to highly-energetic particles or waves that can detach (ionize) at least one electron from an atom or molecule. Ionizing ability is a function of the energy of individual particles or waves, and not a function of their number. A large flood of particles or waves will not, in the most-common situations, cause ionization if the individual particles or waves are insufficiently energetic.

Examples of ionizing radiation are energetic beta particles, neutrons, and alpha particles. The ability of light waves (photons) to ionize an atom or molecule varies across the electromagnetic spectrum. X-rays and gamma rays will ionize almost any molecule or atom; far ultraviolet light will ionize many atoms and molecules; near ultraviolet and visible light are ionizing to very few molecules; microwaves and radio waves are non-ionizing radiation. Visible light is so ubiquitous that molecules that are ionized by it will often react nearly spontaneously unless protected by materials that block the visible spectrum. Examples include photographic film and some molecules involved in photosynthesis.

If enough ionizations occur in a biological system, they can be destructive, such as by causing DNA damage in individual cells. Extensive doses of ionizing radiation have been shown to have a mutating effect on future generations arising from the individual receiving the dose.

Molecular Genetics

Molecular genetics is the field of biology which studies the structure and function of genes at a molecular level. The field studies how the genes are transferred from generation to generation. Molecular genetics employs the methods of genetics and molecular biology. It is so-called to differentiate it from other sub fields of genetics such as ecological genetics and population genetics. An important area within molecular genetics is the use of molecular information to determine the patterns of descent, and therefore the correct scientific classification of organisms: this is called molecular systematics.

Along with determining the pattern of descendants, molecular genetics helps in understanding genetic mutations that can cause certain types of diseases. Through utilizing the methods of genetics and molecular biology, molecular genetics discovers the reasons why traits are carried on and how and why some may mutate.