Copying or using any statement in this article without citing the author and the source where it was taken is extremely prohibited.
The Role of the Environment: A Twist in Genetic Expression
By: Prof. Isidro T. Savillo
Savillo, I. 2003. The Role of the Environment: A Twist in Genetic Expression at http://www.oocities.org/gene_environment2/index.htm
or at BIOLOGY BROWSER: Subjects:Genetics
The environment has a greater role in genetic expressions (Savillo, I, 2002) and these are supported by various findings directly or indirectly. The development of certain organisms or living cells, embryonic or not, are very much influenced by their surroundings. The addition of a little acid to the developing sea urchin did not allow the first step in its independent development (gastrulation) to push through (Tobin, 1999). Transplanted cells during the early course of development, evolved in accordance to the new rather than the old milieu. After gastrulation, this phenomenon ceased and the predetermined fate of transplanted cells began to unfold (Tobin, 1999). Time, an endogenous environmental factor (Savillo, I. 2002), is one of those elements, crucial (Tobin, 1999) to development. Wilt and Hake (2004), stated that cell division gives rise to dissimilar daughter cells. In this manner, the exogenous environmental factors (Savillo, I., 2002) representing the surrounding medium and the endogenous environmental factors of the mother cell may have influenced the differences in the constitution of the endogenous environment of each of the two daughter cells.
The effect of environmental influences are known to manifest over time especially the phenotype on “structural framework.” Nevertheless, there are situations that these three phenotypes (behavior, physiology of cells and structural framework), respond easily to new environmental introductions. Development in new behavior will be experienced after favorable immersion (endogenous environmental factor) to a peer group (exogenous environmental factor). Eating high cholesterol foods (exogenous environmental factor) will subsequently affect negatively the circulatory system of someone whose cells (endogenous environmental factor) are not sufficiently provided with high density lipoproteins to remove cholesterol from blood. A species of fish (Oreochromis sp.) , male in nature, could eventually develop (endogenous environmental factor- pls. see discussion on next paragraph) a female sex organ (ovary) and subsequently produce female gametes ( eggs ) upon application of a female hormone (exogenous environmental factor) (Mair et al, 1997).
The plasticity of sexual phenotypes are mainly due to environmental influences. A number of fish species ( in Family Serranidae, Ictalurus sp., Oreochromis sp., etc.) ( Davis et al, 1990) , ( Doi et al, 1991) , (Savillo, I. 2000) can develop new sexual phenotypic characteristics by changing into a different sexual organ. The environmental factors such as changes in temperature (Streussman and Patino, 1995) or the application of male or female hormone, are protagonist for this change to occur. Two female desert lizards were known to reproduce successfully in nature ( from “The Battle of Sexes” of the Discovery Channel). It seems that the male and female sexual phenotypes are not constant determiners for sex and are very much dependent on their environments. There seems to be a gene or genes (e.g. it can be independent of or found within the sex chromosomes), unfortunately plastic, which could regulate the appropriate sexual phenotypic characteristics of these organisms. This proposed sexual phenotypic gene(s) could determine whether in a particular environmental situation, these organisms would have male or female sexual phenotypic characteristics by developing a new sexual behavior (male to female or vice versa) and producing a new sexual organ (male to female or vice versa) and subsequently, changing its gametes ( spermatozoa to eggs or vice versa). Unfortunately in higher forms of animals, a change in sexual phenotype is limited only to the development of a new sexual behavior (male to female or vice versa), transparent or not, towards the sex of interest. No changes in reproductive organs could naturally occur. The change in sexual phenotype would either lead to a successful reproduction or just casual to serious “unproductive” relations which are species specific. The proposed sexual phenotypic gene(s) could be one of those conserved DNA complexes or remnants of it, which has a role in reproduction and evolution, and was observed to be functional in some lower forms of animals.
On the other hand, a monozygotic sibling was observed to manifest Alzheimer disease while the other twin sibling did not (personal communication). This can be attributed to the differences in exogenous and endogenous environmental factors on which they were subjected. The affected monozygotic twin did experience environmental factors which most likely lead to Alzheimer.
Another absorbing phenomenon was about the glued relationship between a mother and a son who both possess the manifestations of insanity. The unkempt mother has been in this mental status, living on street nooks, before she became pregnant and she raised her son on her own with very little intervention from “normal” individuals ( e.g. limited only to their responses to food begging, etc.) It is amazing that they live completely on their own world/culture that only the two of them can understand. Usually, insanity is an individual culture in open streets and not shared. The mother represents the exogenous environment and was effective in infusing her “own culture” to her son’s growth and development.
The mechanisms of environmental influences could stop, modify, passively allow , change the course of , etc., genetic expressions. In any phenotype produced , it is advisable to know the specific environmental factors (e.g. common and exotic ones) responsible for these changes to occur. This will lead to a more comprehensive understanding of the acquisition and progressive development of a phenotype in an individual and likewise, this would pave way to the meticulous characterization (e.g. molecular, environmental, etc.) of the phenotype in question.
Literature Cited:
Davis, Kenneth B., B. A. Simco, C.A. Goudie, N.C. Parker, W. Cauldwell and R. Snellgrove. 1990. Hormonal sex manipulation and evidence for female homogamety in channel catfish. General and Comparative Endocrinology. 78: 218-223.
Doi, M., M.H.M. Naui, , R.N.L. Nik and T. Zulkifli, 1991. Artificial propagation of the grouper, Epinephelus suilius at the marine finfish hatchery in Tanjung Demong, Terengganu, Malaysia, Department of Fisheries, Ministry of Agriculture, Malaysia 50628 Kuala Lumpur.
Mair, G.C., J.S. Abucay, D.O.F. Skibinski, T.A. Abella and J.A. Beardmore. 1997. Genetic manipulation of sex ratio for large scale production of all male tilapia, Oreochromis niloticus. Can. Journal of Fisheries and Aquatic Sciences. 54, 396-404.
Savillo, I. 2000. Fish Biology and Ichthyology. A Module for Graduate Students.
Savillo, I. 2002. The Overpowering Influence of the Environment to Gene Expression. at http://www.oocities.org/gene_environment/index.html
Savillo, I. 2002. The Overpowering Influence of the Environment to Gene Expression at http://www.biologybrowser.org/bb/Subject/Genetics
Streussman, CA. and R. Patino. 1995. Temperature Manipulation of Sex Differentiation in Fish. In Goetz , F. and Thomas, P. (eds.) Proceedings of the Fifth International Symposium on Reproductive Physiology of Fish. Austin, Texas. p 153-157.
Tobin, A. J. 1999. Amazing Grace. Sources of Phenotypic Variation in Genetic Boosterism. In Carson, R. and Rothstein, M. (eds.) Behavioral Genetics. The Clash of Culture and Biology. Johns Hopkins University Press pp 1-206.
Wilt, F. H. and S. C. Hake. 2004. Principles of Developmental Biology. W. W. Norton and Co., pp 1- 430.
-0-