BIO 102 Principles of Biology

Objective: To examine the effects of mutagenic agents on growth development of organism and to composed and argue a perspective on the topic of effect of mutagens on organism in a formal written paper

Overview

Ever since the discover of natural radiation by Becquerel in 1896, humans have attempted to find uses for radiation and radioactive materials. In science and medicine, x-rays gamma rays’ machines, Cobalt-60 and many other radioisotopes are used to treat, to diagnose or to help find the answers to fundamental research problems. IN the production of energy, humans are looking to atomic reactors as a way of producing energy to drive electric generators. Weapons research has led to nuclear bomb detonations and the emission of radiation from detonation sites. Every time ionizing radiation is produced, whether for good or ill. The risk of exposure to this radiation is increased. Therefore, the effects of increased exposure to ionizing radiation should be of concern to out society.

First, the term ionizing radiation should be explained. Ions are any electrically charged atoms or groups of atoms which can act together as a unit (e.g., the hydroxide ion, OH-) Any radiation that can produce ions would be considered ionizing radiation.

Gamma radiation is a form of energy like X-rays which along with other forms of radiation are emitted from a variety of environmental sources. Two other kinds of radiation are alpha radiation and beta radiation. Beta radiation consists of rapidly moving elections and alpha radiation consists of rapidly moving particles that are composed of two protons and two neutrons. Atoms of the same element that differ from one another in the number of neutrons present are called isotopes. Some isotopes of atoms, such as cobalt-60 are natural sources of gamma radiation. X-ray machines and nuclear power reactors are also sources of gamma radiation.

The method by which protons of e-or gamma rays cause ionization is by colliding with and ejecting an electron from an atom or molecules which is that left positively charges. The ejected electron does not exist for very long in an isolated state, but quickly associates with another particle, forming a second, negatively charged ion. The two ions make up and ion pair. It should be noted that if the energy of the electron that is ejected from the first substance is great enough, the electron will not be immediately captured, but will collide with and eject other electrons from their orbital in other particles until it has lost sufficient energy to be captured. The electrons that have been ejected by the initial electron produced during the primary ionizations process will form secondar ion pairs. Ejected neutrons, protons and alpha particles may also initiation ionization and thus form ion pairs. The fact that different types of ionizing radiation expend their energy in different ways and at different rates can be very important to living organism. For example, alpha particles expend five thousand times more energy per unit length of path than x-rays of comparable energy. Because of this, the most energetic alpha particles would not be able to pass through the dermal tissue in human skin. Should an alpha particle find its way into a living organism, the fact that it could produce millions of ion pairs within a very small volume would make it potentially much more dangerous than either x-rays or gamma radiation of comparable energy.

In studying the biological effect of ionizing radiation, one should be able to determine how much radiation has been absorbed by all living organisms. One of the main units used is the roentgen, which is a measure of the energy absorbed from the rational by a unit volume of the substance being irradiated. One roentgen is said to be delivered to one cubic centime of air when a certain number of ion pairs (2.08X10⁹) has been formed. The energy equivalent of this number of ion pairs is 83.3 ergs. The number of ergs will vary with the type of substance being irradiated, but for biological systems, its has been agreed that one equivalent roentgen is delivered when 93ergs/g are absorbed. This unit is referred to the roentgen equivalent physical or rep. Another unit used is the rad. This unit is equal to the amount of radiation required to bring about the absorption of 100 ergs/g. The rad is equally applicable to all types of radiation and to all biological materials (unlike the roentgen) Most human radiation does are measured in millirads. A third unit that is often used to quantify radiation dosage is the rem (roentgen equivalent man). It is slightly different way of measuring radiation but for gamma radiation the rad and rem are equivalent. Different types of radiation of equal energy would have different biological effects because they would not be absorbed equally in unit amounts of tissue.

With the discovery by Stadler (1928) that exposure o ex-rats and radium induced mutation in barley, scientist began to concern them selves with the effects of ionizing radiation in plants and other organism. Much research has been completed since attesting that growth inhibition and mutation are both results of ionizing radiation. Radiation is of concern because, depending on the type, total amount, or rate of delivery, radiation can cause changes in the genetic material within cells or change the activities of the cells. Many cells have demonstrated that ionizing radiation causes a high degree of chromosomal aberrations. These aberrations could take many forms including, deletions, translocations, bridges etc. and would represent genetic anomalies that could be responsible for subtle or gross changes in the irradiated organism or its offspring. IN this regard, it has been well established that no level of ionizing radiation is too small to produce chromosomal damage. In very high does, ionizing radiation kills cells directly. Although it is undoubtedly true that most mutations are harmful, some beneficial mutations have been brought about using radiation.

In conclusion ionizing radiation should be considered a tool, but a dangerous one. The problems generated by increasing background radiation (natural and human produced) as well as the rapidly growing quantity of atomic wastes generated by nuclear reactors, cannot be overlooked if humans are to avoid a crisis.

Over the course of the next two weeks, you will investigate the effect of ionizing radiation on plants, animals, and humans. You will research papers from peer reviewed journals and produce a 10-page written essay on the topic of the effect of mutagens on DNA