Epigenetic and Sexual Orientation Research Paper

Introduction

Sexual orientation forms one of the most significant variations in human sexuality. Most of the people in any particular population are heterosexual meaning they are attracted to individuals of the opposite gender; males get attracted to the females while the females get attracted to the men. This situation is regarded as the typical occurrence in virtually all societies across the world, but a small portion of the human population is bisexual or homosexual. They get attracted to individuals of similar sex. While some communities view heterosexual and homosexual as immoral, scientists have attempted to uncover why some people go against the usual trend of opposite-sex attraction and instead get attracted to people of their gender (Vrangalova et al, 2012). This paper aims to expound on the role of genetics in sexual orientation.Genetics forms one of the most widely studied areas in biology. As in other areas of applied biology, concepts require backing by evidence from experiments or ideal research conducted using appropriate methods. The paper will start by highlighting proof that shows genetics dictates sexual orientation. Studies of monozygotic and dizygotic twins will be reviewed with the assumption that monozygotic twins show concordant sexual orientation than in dizygotic twins. These studies indicate that some sections of the genome dictate sexual orientation. The paper will also discuss various phenomena to show that biological aspects have an impact on sexual orientation with a possibility of involvement of epigenetic mechanisms among other genetical developments that affect sexual chromosomes and their genes resulting into changes. These changes are responsible for the occurrence of sexual orientations against what is considered normal (Balthazart, 2018). The study will highlight the presence of Xq28 in homosexual male as the unique gene responsible homosexual orientation leading to attraction to same sex. This gene is described as maternal and not paternal gene (Ngun & Vilain, 2014). The gene is unique in homosexual individuals and specific to some families that show clusters of homosexual men.

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In highlighting the connection between sexual orientation and epigenetics, the paper will look at the existence of women with a condition called congenital adrenal hyperplasia (CAH). The affected females usually get exposed to an abnormally high amount of utero testosterone that influences their homosexuality orientation compared with women devoid of CAH condition (Meyer-Bahlburg et al, 2008). Research using animal models will be highlighted to show that long-term effects as a result of inappropriate hormonal exposure are due to epigenetic mechanisms. In synopsis, the paper concludes by stating that genetics have an impact in determining sexual orientation in humans.1.1 Genetics of Sexual OrientationSexual orientation is a significant indicator of sex differences in human beings. While the majorities are heterosexual, few people are bisexual or homosexual. Understanding of the preferences in sexual attraction is one of the primary indicators used in classifying a person's biological sex. It is cited as the most reliable predictor of sexuality after gender identity based on the anatomical structures of human beings. About 2-6 percent of the populations are classified as homosexual. When sex orientation is compared based on the two extremes of being entirely homosexual or completely heterosexual, more women are reported as attracted to their sex as well as opposite-sex as compared to men who only get attracted to one sex (Vrangalova & Savin-Williams, 2012).Research on the connection between genetics and sexual orientation is not new. During mid 19th century, scientists believed that there was a connection between the brain and bodies to homosexual orientation. As science advanced, scientists were able to link homosexual and defective development. In early 20th Century, the bodily appearance of homosexuals was significant interest, and they were classified as a third category of gender in addition to male and female gender. Gay men were thought to have natural female behavior while lesbians appeared masculine. In the current world, homosexual is not classified as a distinct gender, but the reverted sexual pattern has a significant impact on the direction taken by research on homosexual aspects especially on the neurological correlations (Ngun & Vilain, 2014). Genetical facts form the base of most recent studies attempting to explain the occurrence of sexual orientation.

1.1.1 Twin Study

The first indication that genetics could be the major influencing factor in sexual orientation came from studies of families with gay individuals. Results showed that gay people had a higher number of relatives who were homosexual men compared to heterosexual men. Similarly, homosexual individuals had a clustering of homosexual relatives in their families. Another study that showed a significant connection between genetics and sexual orientation was called "twin study." This study compared sexual orientation in monozygotic twins and dizygotic twins. Monozygotic twins are identical twins that develop from one fertilized egg called zygote that splits to form two identical embryos while dizygotic twins result from two eggs that are inseminated by different sperms. Identical twins have a higher percentage of similar genes than dizygotic twins. Results showed that chances of two identical twins assuming similar sexual orientation were higher than for the cases of dizygotic twins (Balthazart, 2018). These studies suggested that sexual orientation is heritable through genes.

1.1.2 Specific Gay Genes

Several molecular genetics studies were conducted in gay men to confirm that genes form the core factor in sexual orientation. A survey conducted in 1993 by Dean Hamer and associates implicated homosexual gene in connection to a specific gene locus. They noticed male homosexual were clustered in particular families and hence decided to focus their analysis on the X chromosome that is specific to the male gender. They discovered that male sexual orientation was directed to genes located at the terminal of X chromosome. They named this gene Xq28 gene. Further characterization revealed that Xq28 is a complex, big and a dense gene. This gene was also implicated in other four subsequent studies. Further analysis showed that the gene was more pronounced among homosexual brothers (Vrangalova et al, 2012). However, it is worth noting that Xq28 is only found in homosexual males and not females.

In 2005 a more advanced study was done using genome-wide scanning to detect markers connected to male sexual orientation. This study sampled 400 gay individuals including participants recruited in the previous studies. The subjects used in the early research showed the presence of Xq28. Analysis of all participants including the newly recruited revealed the presence of some associated genes at chromosome 7 and 8. These genes were (7q36) and (8p12) respectively. Gene called 10q26 was also detected at chromosome 10, and linked to homosexual orientation; however, this gene is connected to inherited alleles (Ngun & Vilain, 2014). Such genes were as a result of mutations that are subsequently passed to the offspring.

Although biological aspects that influence sexual orientation may vary between sexes, the genetic factors behind these traits are likely to be similar. It is likely that homosexual genes work similarly in both males and females. Due to the close connection between sexual orientation and biological sex, there is a likelihood that the same aspects that influence sexual factors in other areas of sexual development are also the ones dictating the direction taken by sexual orientation. In most cases, neural development is canalized in a way that predisposes them to be sexually attracted to individuals of their sex. Despite these proceedings, both genetical and nongenetic factors can connect to the developments to influence the outcome in varying ways. A good example is how the high levels of the hormone can affect the genetic events in mechanisms such as epigenetic to alter the genetical marks (Balthazart, 2018). In such cases, opposite sex-typical developments may arise leading to attraction to own sex.

1.2 Epigenetic and Sexual Orientation

Epigenetic refers to the changes that occur in genes and subsequently expressed. The changes in epigenetic mechanism do not involve the present DNA sequence. In essence, the process affects phenotypes without affecting the genotypes but affects how the cells read the genes. The occurring changes are heritable and passed from parents to their offspring. Environmental influences affect the biological aspects through the mechanism of epigenetics. The study of twins and their sexual orientation discovered that the exposure to different environmental factors such as intrauterine conditions during development could affect their variations in sexual orientation. Although most of the environmental factors such as nutrients may be similar in most twins, other factors could influence epigenetic factors leading to effects on the sexual orientation genes. It is already known that monozygotic twins do not have similar DNA methylation during birth. Discordance in monozygotic twins in some traits is as a result variation in DNA methylation (Balthazart, 2018). This aspect could be the primary factor leading to differences in sexual orientation in monozygotic twins.

1.2.1 Inherited Homosexual Genes

Other research findings have indicated a significant relationship between the effects of utero environment and the resultant sexual orientation. Fraternal birth order effect is widely studied in sexual orientation research. Research shows that each son of a homosexual father has recorded a 33% increment of a likelihood of becoming homosexual as compared to the proceeding son. Although this rate seems like a significant increment, the possibility of a homosexual son only attains 50% likelihood if there other ten sons born before. This phenomenon is only valid if all the male offspring are from the same mother. The number of sisters does not have any influence in this scenario. There has been a suggestion that male-specific antigens are triggered in the womb, and every subsequent pregnancy of a male increases its immune response against the antigen (Balthazart, 2018). Regardless of whether this suggestion is valid, epigenetic mechanism influences long-term effects of the utero events.

The presence of 10q26 gene in male chromosome strongly suggests the role of epigenetics in homosexuality. 10q26 is only connected to homosexual in situations where there is sharing of alleles of maternal origin in excess. Genetic fingerprinting reveals that this gene is methylated in a germ-line connected to parental origin. There are epigenetic mechanisms that are specific for X chromosomes. Such processes are also connected to sexual orientation aspects. In people who have two copies of X chromosome, one copy is deactivated such that the X gene dosage will be similar to people with just a single copy. The choice of inactivation is usually random in cells accruing at 50% for both maternal X chromosome and paternal X chro...