Homosexuality: a case of Epigenetics?
Brain Development. Central Nervous System. Neurons. Nucleutides. CpG Island. Sexual Differentiation. DNA Methylation. Histone Modification. Neurotransmitters. Hormones. HPA Axis. Epigenetic Marks. Epigenesis.
Science has proven that there is no such thing as Gay gene(s). The completed "Human Genome Project (HUGO)" found no Gay genes. Experts opined that since it is not genetically controlled it is a kind of sexual orientation or popularly known as "Choice". Therefore, the cause of homosexuality is based on the interplay of various non-genetic factors i.e. environmental in nature.But, homosexuals counters that it's not a choice, "we are born this way", it is innate because, despite the homosexual therapy, the person remained homosexual.
By nature, homosexuality is the attraction to the same sex (male-male or female-female relationship) It is an enigmatic and complicated issue. Moreover, Homosexuality is not new, it is an old issue. In the Old Testament of the Holy Bible, homosexuality is already mentioned in the Book of Leviticus (Lv 20:17) that God forbids it, because it is a sinful act and violates God's commandment of procreation by declaring that man and a woman is joined together to become husband and wife in order to produce children, homosexuals cannot fulfill this heavenly mandate. But, why they do persists? Attendant to this is the argument that, if homosexuality is biological in nature, they could have been extinct long time ago? For the reason that they cannot transfer their genetic endowment to the next generation. Although, in some animals and social insects, "Kin Selection" is practiced to improve the reproductive success of the colony or group, but humans are not animals nor insects
The origin of Homosexuality is not fully understood by scientists and therefore, subject to a hot debate. The theories about homosexuality fall into two broad categories i.e. as theories that point to Nature (biological variables) and as theories that pertain to Nurture (influence of experience, and of psychological variables) that yielding to ultimate harmful desires and which choice is partly affected by nurture and environment. So, let Science proved it, instead of opinions based on Religion, Family, or Culture. Nevertheless, it won't matter whether this is caused by nature or nurture because either way, Homosexuality is a fact.
Humanity at the crossroad.Humanity is divided on the issue of homosexuality. Conservatives that adhere to church teaching condemns homosexuality as a sinful act by violating God's purpose of creating man and woman for the porpuses of procreation The liberals are quick to depend on their stand by stating that, they are not against homosexuality, but its what they do that tend to send young men to an early grave due to AIDS/HIV attack, while the post-modern man takes a humanitarian stand on homosexuality by evoking freedom and liberty that no one should be deprived of happiness regardless of gender, color, creed or belief.
What they say about Homosexuality
The ancient biological story of man originated in the ancient Scriptures when the Divine Creator breath life to an inanimate object. The Holy Bible being the most Comprehensive transcendent moral Authority, abundantly deals with human nature and behavior and consistently manifest that the nature of man has not changed since the Fall (Conservapedia, 2015). The Biological man has been provided by God, of things for his survival and propagation of his species.The man was given the gift of knowledge and wisdom to decide what is wrong and what is right and thus the battlefield for Good and Evil rest on the mind of man.
The World Religions
Major world religions: Judaism, Christianity, Islam, Hinduism, Buddhism, Sikhism, Jainism, Confucianism, Daoism among others considered Homosexuality as unnatural, abhorrent, to God and not leading to human fulfillment.
Since the dawn of human history, Homosexuality has been practiced and encouraged by society from Ancient Egypt, the Greeks, and Romans, African savanna, Native American Tribes and to the middle of Pacific, the Polynesians among others. Homosexuality as a sexual desire, pleasure of the flesh, a trade, to gain education(Pederasty), an evolutionary insurance for those who breed by caring for the young
Humanity, in general, takes a tolerant attitude towards Homosexuality in this modern society. Moreover, issues pertaining to Gay marriages is still being debated and Church conservatives opposed to this union
Origin of Homosexuality
A prominent 19th-century, Neurologist, and Psychologist, Sigmund Freud (1856-1939) contend that all children go through a stage of their psychosexual development when they are bisexual and have the potential for either heterosexual or homosexual expression from which they formally make the association to homosexuality in adulthood.Those who turn to Homosexuality as an adult, Freud, believed have experienced some traumatic event that arrested their sexual development. Contemporary, Psychologist, moreover, look as problems within parental and family dynamics in childhood that create issues on gender identification later in life (New World Encyclopedia,2015)
Another, prominent 21st-century Psychologist and Neuroscientist, Simon LeVay, was criticized and misinterpreted because of the results of his research on Homosexuality, but in LeVay's words:
"It is important to stress that what I didn't find, I did not prove Homosexuality was genetic, or find a genetic cause for being gay. I didn't say that gay men are born that way....since I looked at adult brains we don't know the differences I found were there at both or may appeared later"
LeVay's result's was criticized for having found a gay gene, but his statement above clarified the issue.
If it wasn't genetics and if it wasn't environment (upbringing), then what could it possibly be? The answer is the prenatal environment, the result of something that occurred as the fetus develops in the womb expert said.
The search for a New Meaning
If nature and nurture could not provide a satisfactory answer to Homosexuality, there must be other explanation into this, An emerging field of study on Neurobiology and Psychological Genetics offers a vibrant field of study on Homosexuality called Epigenetics. In a nutshell, Epigenetics offers a mechanism for regulating gene activity independent of DNA sequence that determines which gene(s) are turned on and off. Though this article seems highly speculative but the elements are there to provide an answer to the complicated and enigmatic nature of Homosexuality.
Epigenetics is an incredible field of study that encompasses a whole array of cellular processes. Some Epigenetic mechanism includes DNA methylation, Histone modification, Genomic imprinting, Non-coding RNA's, and X-chromosome inactivation. These results in changes in organism cell types, including cellular differentiation. Basically, Epigenetics is a blanket term used to described any type of Cell memory passed into offspring that does not involve direct manipulation of the DNA sequence.
Epigenetics is the study in the field of Genetics, of cellular and physiological phenotypic trait variations that are caused by external or environmental factors that switch genes on and off and affects how cells read genes instead of being caused by the changes in the DNA sequence
Hence, the Epigenetic research seeks to describe dynamic alterations in the transcriptional potential of the cell. This alteration may or may not be heritable, although the use of Epigenetics to described processes that are not heritable are quite controversial unlike Genetic based changes in gene expression as cellular phenotypes of Epigenetics have other causes, thus the use of the prefix pre (Greek=over, outside or around) to described non-genetic causes other than changes in the DNA sequences.
Paradigm shift: The theoty of Epigenesis
The originator of the Theory of Epigenesis was Aristotle (384-322 B.C) in his book on the "Generation of Animals" though the theory seems obvious in today's genetic age, nevertheless, the theory was not given too much credence in former times because of the dominance for many centuries of "Creationist Theories" of life origin. Moreover, during the 18th-century, an extended and controversial debate by Biologists finally led Epigenesis to eclipse the long established "Preformation view". The Embryologist Caspar Friedrich Wolf (1734-1794) famously reputed Preformationism in favor of Epigenesis ( Wikipedia, the free encyclopedia)
In recent years, however, it has become increasingly clear that cellular inheritance is not limited to simple Mendelian genetics, the term Epigenetics has been used to described these types of inheritance that are not due to changes in DNA sequence, yet result in a new trait being passed from parent to offspring.
When Waddington (1905-1975) coined the term in 1942, the physical nature of genes and their role in Heredity was not known, he used the term as a conceptual model of how genes might interact with their surroundings to produce a Phenotype. He used the phrase "Epigenetic Landscape" as a metaphor for Biological development. Waddington, hold that cell fates were established in development much like a "marble" rolls down to the point of lowest local elevation (Wikipedia, the free encyclopedia) Furthermore, the developmental psychologist, Erik Erikson (1968), used the term Epigenetics Principle in his book "Identity: Youth and Crisis" and used it to encompass the notion that " we develop through an unfolding of our personality in predetermining stages and that our environment and surrounding culture influence how we progress through those stages".
Cells of multicellular organisms are genetically identical but structurally and functionally distinct owing to the differential expression of genes. Many of these differences in gene expression arise during development and are subsequently retained through Mitosis. The term Epigenetics is now commonly used to describe the study of Stable Alterations in gene expression potential that arose during development, differentiation, and under the influence of environment. In contrast to DNA sequence that is identical to all tissue, the pattern of Epigenetic marks is tissue specific. Hence, the Genome (total genetic material found in a living cell )can be considered to contain two layers of information i.e. the DNA sequence inherited from the parent which are conserved throughout life and mostly identical in all cells and tissues in the body, and Epigenetic marks i.e. Chromatin and DNA methylation patterns which are cell and tissue specific.
Finding the SWITCH ?
It appears that from the beginning, Epigenetics violates Mendelian Genetics i.e genes are passed from generation to generation unchanged and offsprings were alike genetically, depending on the nature of the genes (dominant or recessive) contributed by the parents, in other words, the DNA sequence of the gene is unchanged. In contrast, Epigenetics afford the appearance of new phenotypes without the involvement of DNA. Conversely, Epigenetics does not conform with the Central Dogma of Biology, therefore, one may ask, where will Epigenetics start? The most likely place is after fertilization. The Zygote (Diploid=2n) the fertilized egg, receives its genetic endowment from its mother(egg=haploid=n) and father(sperm=haploid=n)and whatever genetic information contained in the genome of its parents including Epigenetic marks are also transmitted from the parents to the offspring and those induced by prenatal events and other parental Epigenetic marks. Even at the Zygotic stage, the "memory" of these Epigenetic marks such as DNA methylation and Histone modification are already copied to primary cells or stem cells (eg.two-cells stage) in the Zygote and this information is passed on to the succeeding generations of cells, Mitotically (somatic), to assume various cellular functions in the development and growth of the organism in later life. These alterations may turn on or off some genes at later life that may affect also the Phenotypic appearance of the individual. Likewise, Epigenetics denoted Biological inheritance above the Genetic level that may affect children's phenotype beyond DNA sequence including sexual behavior.
The Route to HOMOSEXUALITY?
Though this paper appears quite speculative at the moment but the knowledge and possible applications to the future is immense. While the application of Epigenetics to underscore the complexity of Homosexuality is being debated due to the dearth of information at the present, but it does not mean that we will not reach the end of the road, since Epigenetics is dynamic and evolving science. At the moment, the question, What are the predisposing factors or events that will possibly lead to Homosexuality is being searched and studied, for instance, the mechanism of Epigenetics. There are 3 major mechanisms of Epigenetics, namely, DNA Methylation, Histone Modification, and Micro RNA-DNA Methylation. DNA methylation and Histone modification are the most common form of Epigenetic mechanism.
Biologist, Robin Holliday (1990) defined Epigenetics as the study of Mechanism of temporal and spatial control of gene activity during the development of complex organisms. This Epigenetic mechanism can be used to describe other than DNA sequence that influences the development of the organism. It is already well-known that children inherit their DNA sequences of Nitrogenous Bases, namely, Thymine (T), Cytosine (C), Guanine (G), and Adenine (A) from their parents, However, children can inherit more than just DNA sequence, they can also inherit Methylation marks which affect which part of the Genome are actually read or repressed and may affect the children's Phenotype even more than DNA sequence
DNA Methylation-the CODE of Silence
DNA methylation involves the addition of a Methyl group (-CH3) to DNA nucleotide. This methyl group often attaches to Cytosine (C) residues in the DNA double helix. In mammals and other vertebrates, 1 out of 100 nucleotides bears an added methyl group which is always attached to carbon 5 of the Ribose sugar of Cytosine. this chemical modification does not affect the base pairing ability in DNA, so it does not alter the Genetic Code. Additionally, the methyl group is always added to the 5th carbon of Cytosine in C- G sequence. The dinucleotide C-G is a common target by the specific enzyme called Methyltransferase forming in CpG configuration (Phosphorylated=P is added). This methylated Cytosine can be inherited because a specific enzyme called Maintenance transferase uses the parent DNA strand the template to methylate the daughter strand during DNA replication. These methylated nucleotides can be inherited from the parent organism (a form of Epigenetic inheritance), Epi- (in Greek, meaning Over or Above ) genetic, or may also arise new in the organism own lifetime.
Histone Modification-the TAILS of HISTONES
An equally important Epigenetic mechanism is Histone modification. Histones are proteins that bind DNA in Eukaryotic Chromosome forming a structural unit called Nucleosomes. These Nucleosomes are in turn packaged together to form the Chromatin. The Chromatin includes the Chromosome which is bounded by Histones and non-Histone proteins. These Histone proteins are extensively modified at their N-terminal tails by Methylation, Phosphorylation, Acetylation, and Ubiquitination as part of the Histone signature serving to define accessibility to the DNA i.e. densely packaged "closed" chromatin called Heterochromatin and accessible "open" Chromatin called Euchromatin. The former denote "repressed" gene action (inactive) while the later denote "expressed" gene action (active).
The Brain, Neurons, and Neurotransmitters
If Homosexuality started during pregnancy, then both identical twins will have the same phenotype, but it was not, this simply implies that having two different phenotypes i.e one Straight and one Gay is non-genetic in the sense that the two develop from one fertilized egg and the same amount of DNA. this tends to suggest that another mechanism is operating that influenced the variation among phenotypes. if we connect Epigenetics which is the nearest possible cause of Homosexuality, again it's too early to tell since it is expressed in the later life of the individual and, what is more, confusing is, it become behavioral rather than biological. The most likely place to find an answer is in the Brain.
When the man was born, the mind is Tabula Rasa (in Greek means Blank slate), as the man grew the brain collects experiences from the environment and store this into memories and go to the motion of cognitive processing an important input for man's survival. Similarly, these experiences may later influence the expression of Homosexuality. While the Genes provide the blueprint for the Brain development, however, it's the child's environment and experiences that carry out the construction. According to experts, human brain begins to develop from conception to age 3, it is at this stage that the number of synapses is doubled precisely to accommodate the cascades of experiences that the child received from the environment. The environment of a child's earliest years can have effects that last a lifetime (The Urban Child Institute, 2016)
The Cental Nervous System (CNS) is the most complicated nerve system of the human body. Composed mainly of neurons that criss-cross every nook and crevices of the human body to deliver vital messages from the network of approximately 100 billion neurons At the very center of this sophisticated network of neurons is the Brain, the communication center of the human body. To deliver complex messages, three important neurotransmitters take turns in delivering messages via electrical impulses, namely, Norepinephrine, Dopamine, and Serotonin, In addition, a combination of neurotransmitter Dopamine and Serotonin in the Brain affords the expression of phenotypic traits such as Sex (sexual behavior, attraction to opposite sex or same sex), Appetite (food, sex, etc.) and Aggression a male trait copied from the Y chromosome. While Dopamine is quite delimited to the fore and middle brain, Serotonin projection almost ramifies in the different regions of the Brain. At fertilization, during the union of sperm and egg, experts believed that whatever Epigenetic marks borne by both parents is passed on to the Zygote (fertilized egg) and embedded as "memories" in the generations of different cell types as the fetus develops in the womb. Moreover, Epigenetic marks may be also generated in the fetus if the mother is subjected to stressful conditions. Remember that at this stage the fetus and the mother are still one through the umbilical cord, whatever emotional trauma experienced by the mother is passed on to the developing fetus. These Epigenetic marks are conserved in the fetus and may be expressed in later life as some Gene(s) are turned on or off at the specific stage of development vis a vis sexual behavior. Homosexuality is supposed to manifest at the pre- puberty stage when pubic hairs start to emerged from the genitals (9 to 12 years old) and it is during this stage that the supremacy between the two Hormones i.e. Estrogen and Androgen become apparent
Mode of Actions-The Gay Brain
While Homosexuality is expressed in later life, it's impression has been marked already after fertilization or during conception. It is a common knowledge that some genes are turned on and off at the specific stage of development while others are not. At puberty stage, sexual orientation is redefined, for instance, Straight (Heterosexuals) or Gays (Homosexuals-male or female) and why this is so, one possibility is that Genes in the Sex Chromosome X and Y are not active or transcript has been made but cannot be translated into Protein. It appears that nucleotides (CpG) has been methylated or Histones undergone modification. These Epi-marks now awakens from long slumber the genes at the promoter region to turn on the structural genes responsible for the production of a male and female hormone in the X and Y Chromosome respectively. For the normal male, a number of genes in the Y chromosome are enough to initiate the production of Androgen, while Homosexual male has Androgen deficiency, consequently, normal female, requires both "sex genes" in the two X chromosome, inactivation of the other pair lead to imbalanced Estrogen level or none at all if the two alleles are both repressed or may have excess production of Estrogen level (Gunther, 2001). Conversely, the role of environment or experiences take effects and Epigenetic factors superseded over the Genetic factors. The Brain having received the stimulus from Epi- marks, the Hypothalamus send signal to the Pituitary gland to stimulate the Endocrine System via the Adrenal gland (HPA-axis) in the production of a male or female hormone, it appears, however, that male Gays has more female hormone (Estrogen) and excess male hormone (Androgen) in the case of female Gays(lesbian), while normal males received appropriate amounts of both hormones. Phenotypically, it appears that in the case of male Gay's the Brain has been "feminized" conversely, the brain in female Gay's has been "masculinized"
There are three possible routes for becoming a Homosexual, first at Fertilization, second at Conception and third at the Pre-puberty stage. At fertilization genetic constitution from both parents is passed on to the fetus via sex cells (Egg and Sperm) including Epigenetic tags (none- genetic) such as methylated DNA and modified Histone proteins that may later influence Phenotypic expression of Homosexuality.Likewise, parents who have a traumatic experience, disease, exposed to a mutagenic agent may further influence the expression of genes as it passed to the fetus defective DNA sequences. At this point, one must subsume to the idea that Homosexuality is not due to one or two genes but of myriad of genes interacting at the different stages of human development Assuming that the fetus received healthy DNA from its parent, if the pregnant mother is subjected to emotional trauma for the first 8 weeks of pregnancy (1st trimester) may also generate Epi-marks in the developing fetus as traumatic experience (emotion) is passed on via the umbilical cord. the third and the final stage is at pre-puberty as Epigenetic marks are expressed during the synthesis of sex hormones i.e. androgen and estrogen. Differential production of these hormones influenced sexual behavior vis a vis Homosexuality. The brain plays a crucial role in the expression of homosexuality since attraction or desire with the same sex as elicited by sex hormones start from the Brain and consequently, the role of neurotransmitters in passing these signals from Hypothalamus to Pituitary and finally to the Adrenal gland. On the other hand, this account could be too simplistic since Homosexuality is the quetisintial distillation of genetic, environment, and epigenetic factors.
In conclusion, Homosexuality is a complicated and enigmatic nature of human sexuality. As research results from studies reveals that Homosexuality is not only due to genetic or environmental factors alone but could be further elucidated by Epigenetics. Although the understanding of the interplay between genetic modification is still evolving, the modification of core histones and DNA methylation in Cytosine-Guanine dinucleotides(CpG) represent the best understood Epigenetic marks. We hope that Epigenetics can provide conclusive evidence for the cause of Homosexuality and erase the stigma accorded to Homosexuals.
The author wishes to acknowledge and thanks the owner(s) of images/photos used in this article. Likewise, the author(s) of references for sharing their knowledge free of charged and to Hubpages for the opportunity.
- Agnati, L. et.al.2011. Understanding wiring and volume orientation. 2010. Brain Res. Dev. 64(1): 137-59. [PubMed]
- Baby's brain begins now: Conception -Age3. The Urban Child Institute. Retrieved-January 29, 2016.
- Barron, J. 2012. Everything you need to know about Epigenetics. The Baseline of Health Foundation.Retrieved- January 25, 2016.
- Central Dogma of Molecular Biology. Wikipedia, the free encyclopedia.Retrieved-January 24, 2016
- CpG site. Wikipedia, the free encyclopedia. Retrieved-January 24, 2016.
- CpG Sites. Center for Research in Genomic Medicine. Retrieved- January 28, 2016.
- Dalery, J. et.al. 1981. The role of hormones in the sexual differentiation of the Central Nervous System in animal and man. Ann. Med. Psychology (Paris)130(7):721-40 (Abstract)[PubMed]
- Doell, R, 1995. Sexuality in the brain. J, Homosex.28(3-4): 345-54. (Abstract)[PubMed]
- Doner, G. 1981. Sex hormones and neurotransmitters as mediator for sexual differentiation of the brain. Endokrinologie (2-3): 129-138.(Abstract)[PubMed]
- Ferguson-Smith, A. 2011. Genomic imprinting: The emergence of an Epigenetic paradigm. Nat. Rev. Genet. !2(9): 663 (Abstract) [PubMed]
- Garcia-Falqueras, and D. Swaab.2010. Sexual hormones and brain: an interface alliance for sexual identity and sexual orientation. Endocr. Dev. 17:22-35. (Abstract)[PubMed].
- Gunther, D. et.al. 2001. Genomic and Epigenetic effects on sexual brain organization mediated by sex hormones.Neuro Endocrinology Letters.22: 403-409.
- Grandma's experience leave a mark in your genes.2013. Discover: The Science for the Curious. Retrieved-January 25, 2016.
- Homosexuality. Stanford Encyclopedia of Philosophy. Retrieved-January 26, 2016.
- Homosexuality. The New world Encyclopedia. Retrieved-December 2, 2015.
- Homosexuality. Wikipedia, the free encyclopedia. Retrieved-December 2, 2015.
- Homosexuality in the New Testament. Wikipedia, the free encyclopedia. Retrieved-December 2, 2015.
- Human Sexuality. the New World Encyclopedia. Retrieved-December 2, 2015.
- Hypothalamic-Pituitary-Adrenal Axis. Wikipedia, the free encyclopedia. Retrieved-January 30, 2016.
- Jost, J 2008 (ed.). EpigeneticsCaister Academic Press.(www.caister.com) Retrieved-January 28, 2016.
- Khan, Z. Islamic View about Homosexuality. Islam Awareness Homepage. Retrieved-December4, 2015.
- Korey, C. 2008. DNA methylation. Google search. Retrieved-January 26, 2016.
- Makini, B. 2012. Homosexuality's cause isn't Genetics, but lies in the womb.Science Tech. Retrieved- January 22, 2016.
- MacIsaac, T. 2014. Your thoughts control your DNA: Biologist. Epoch Times Article (Feb. 22, 2014)
- Morris, K and J. Mattick. 2014. The rise of regulatory RNA. Nat. Rev. Genet. 6: 423-437. [PMC]
- Norton, E. 2012. Homosexuality may start in the womb. Science AAAS. Retrieved-January 22, 2016.
- Neuroscience. New World Encyclopedia. Retrieved- January 21, 2016.
- Savic, I. et.al. 2010. Sexual differentiation of the human brain in relation to gender identity and sexual orientation. Prog. Brain Res. 186:41-62 (Abstract)[PubMed]
- Sexual abuse being the contributing factor for Homosexuality. Conservapedia. Retrieved-December 4, 2015.
- Sexual orientation.Wikipedia, the free encyclopedia. Retrieved-December 6, 2015.
- Swaab, D. 2007. Sexual differentiation of the brain and behavior. Best Pract. Res. Clin. Endocrinol.Metab. #:431-44.[PubMed]
- Societal attitudes toward Homosexuality.Wikipedia, the free encyclopedia. Retrieved-December 4, 2015.
- The Neuron. The DEA. org. Retrieved- January 25, 2016.
- Why is homosexuality a sin, if Allah made me this way?Islam. Retrieved- December 4, 2015.
- Why does Islam forbid Lesbianism and Homosexuality? Islam question and answer. Retrieved-December 4, 2015.
- Yoder, M. 2012. Is Epigenetic totally gay?Nothing in Biology Make Sense. Retrieved-January 22, 2016'