Genes That May Have The Effect On Violent And Aggressive Behaviours
The field of genetics is vast and has grown tenfold in the last quarter century. Understanding the genome and sequence of DNA has provided a great success in finding and fighting virus’, cancer research, stem cell research and providing outstanding comparative analysis in forensics.
In 2003, a huge modernisation to science was completed – The Human Genome Project. International pioneers in science reached an exciting goal, in completing mapping of all human genes to provide a clearer understanding of human life and function (National human Genome Research Institute, 2016)
DNA or deoxyribonucleic acid is essentially the programming site for all the information required for the human body to develop and function e.g. it will determine eye colour, hair colour, skin pigment and most other features. It is stored in every cell, apart from erythrocytes (red blood cells) and is comprised of a double helix which is made up of four nucleotides – adenine (A), thymine (T), guanine (G), and cytosine (C) . These nucleotides are formed from carbon-nitrogen and are complementary to other suitable base pairs. To illustrate this the sequence ATGCT would form complementary base pairs, TACGA. The base pairs will form a sequence of unique nucleotides which is what separates humans from other animals both intra and inter species (Chao, 2006). Albeit, sometimes a small difference is noted such as the difference between humans and chimpanzees as around 96% of DNA is shared, the remaining 4% accounts for human’s ability to speak, form emotional and complex thoughts and process information. The same principle is applied to that of humans, although the DNA shared is of a larger amount (around 99 percent and 100 percent in monozygotic twins). This remaining 1 percent is what accounts for human variation among individuals e.g. personality traits, behaviourisms and physical characteristics. Additionally, it is this 1 percent which is exploited in a forensic setting to determine individuality among people (The New Genetics, 2010).
Genes are segments of DNA that carry the specific information required to code for proteins. Proteins are made up from long, complex polypeptides which are amino acids. The actual structure and sequence of the amino acids will determine the function of the protein. Knowing this the genomic code can be understood, as genes are a fundamental part of heredity traits. Knowledge of these heredity traits, can clarify what information is passed down from both the maternal and paternal line, this can be certain diseases or mental and physical abilities (Chao, 2006; Genetics: MedlinePlus Medical Encyclopaedia, 2016).
In early years, it was believed that traits were equally inherited from each parent, and that each genotype produced would be a 50/50 from each parent. However, Gregor Mendel in the 20th Century conducted a variety of studies which proved this was erroneous (Castle, 1903). Through the introduction of his laws of inheritance and heredity the Mendelian theory was plucked out of historical obscurity. Mendel birthed conceptualist theories in others, such as Wilhelm Johannsen who coined division between ‘genotype’ and ‘phenotype’. Genotype meaning what the organism may inherit from parents, and phenotype being what is actually expressed in the organism (Waller, 2017). The genotype in the individual is what will determine the characteristics, appearance and mannerisms. However, individual’s observable characteristics can look fairly different depending on inherited conditions and environmental outcomes. The combination of alleles an individual has will determine their genetic outcome (Orgogozo, Morizot & Martin 2015). An organism may either have heterozygous or homozygous alleles such as BB, Bb or bb. Wherein B is the dominant allele and b is the recessive allele. These dominant alleles will affect the phenotype that is expressed in the individual e.g. eye colour, hair colour, height (Wilcox, 2001). The magnitude of the inherited traits will depend on the number of genotypes located on the specific loci, along with any environmental exposures, thus it is seen that traits of conformability tend to be around 0.5 or more (Hill, 2013). In light of this, what can be said for the inheritance of “bad” genes?
SEX CHROMOSOME ABNORMALITILES
Klinefelter Syndrome – XXY Genotype
Klinefelter syndrome (KS) or carriers of an XXY genotype, occurs in 1 in 500 births. There are several genotypes, including XXY (the most common at 47 percent) and XXXY and XXXXY (very rare). Phenotypically, males can display feminine features, including female body structure and breast enlargement. They are also predominately sterile and have small testes and prostate glands, producing little to no testosterone. These hormonal effects can be somewhat curtailed if they are supplemented with growth hormones and testosterone from an early age. Occasionally, they can experience language and memory problems, although generally they are ordinary in mental abilities. However, as many of these symptoms go unnoticed throughout life, most males do not know they suffer from the syndrome (O’Donovan & Völlm, 2017). A study conducted by Stockholm et al, found that sexual abuse, burglary and arson were offences which were frequently committed by people with KS compared to those who did not have the syndrome (Stockholm et al., 2012). KS has been linked to a number of anti-social behaviours, some of which include alcoholism, homosexuality and other sexually deviant behaviours. but yet only a few studies have focused solely on KS (Mosier, Scott & Dingham, 1960).
“Jacob’s syndrome” – XYY Genotype
Although the XXY karyotype has been associated with some forms of crime (Stockholm et al., 2012) most studies have focused instead on individuals who have the XYY or “supermale” mutation, in which males have an extra Y chromosome. In turn males will possess 47 chromosomes instead of the normal 46, this can be because of complications during cell division (Robinson & Jacobs, 1999). Affecting 1 in 1000 new-born males, the XXY genotype is rare and was first reported in 1961, when a male was discovered to carry this gene when he fathered a Down Syndrome child. Following this, there was a surge of reporting amongst males between then years of 1961 and 1965, but only a minute few were actually carried the gene. Conventionally, these males are very tall (over 6 feet), and experience poor coordination, elevated levels of testosterone, facial acne and have a very low IQ, otherwise they appear normal.
In 1966, criminal law was spun into controversy when Richard Speck, who was convicted of murdering eight nurses in Chicago, was also found to possess the extra Y chromosome. However, subsequent appeals were not upheld in a court of law and he was sentenced to death (Horan, 1992). A number of other cases following this showed a similar outcome as although they had the XXY karotype and pleaded insanity, it was not believed to be admissible in court (Bartholamew & Sunderland, 1966; Saxe, 1970). The feature that tends to be most commonly recognised amongst literature in individuals with the XXY defect is that they have ‘low’ intelligence, and have a higher tendency to commit crime. Another feature commonly seen amongst offenders who carry the genotype, is that they are primarily tall, however this cannot be used to explain offender behaviour alone as this is highly prejudice and a genetic outcome which cannot necessarily be controlled. Thus, combined they can portray a causal link between offender phenotypes (Horan, 1992). This paints a frightening picture, in which males who are of a taller stature and lower intelligence level are stereotypically linked to crime and at a higher risk of imprisonment due to bias by law enforcers, and possibly fear (Hunter, 1966). Jacob’s syndrome has been widely associated with behavioural problems, which can give rise to high levels of aggression which is not always the case but can be fairly common. Studies show that those who do display behavioural disorders tend to be unstable, have limited concern for their actions, show little emotional response, little empathy and compassion for others and aggressive outburst are commonly seen (Price & Whatmore, 1967). Furthermore, when socioeconomic parameters are taken into consideration it is seen that the characteristics of the XYY karyotypes are much closer to that of the controls (Stockholm et al., 2012). Despite the fact that some studies have argued there is a link between this genotype and aggression, the majority of studies have disproved this with only slight bouts of antisocial behaviour seen in smaller populations (Götz, Johnstone & Ratcliffe, 1999). Overall, it can be argued that the majority of population data seen is relatively biased, with individuals who display certain phenotypic characteristics e.g. height and IQ levels being targeted. Many studies also have failed to take into account mental instability unrelated to the karyotype which may affect behaviour outwardly but separately from the gene (Walzer, Gerald & Shah, 1978), lastly as most criminal cases using XYY karyotype were inadmissible in court, it would seem fair to doubt the authenticity behind the evidence.
DOPAMINE AND SEROTONIN POLYMORPHISMS
Genes associated with brain functioning have received some promising outcomes in regard to the effect they may have on violent and aggressive behaviours. Minor infirmities in the brain have been correlated with negative mannerisms such as gambling, minor addictions (Boutwell, et al., 2014). It can be understood that the etiopathophysiology of aggression is wildly misconstrued amongst literature. Amongst the polymorphisms allied with violence and aggression are dopamine and serotonin.
Dopamine
Dopamine, 4-(2-Aminoethylbenzene-1,2-diol (DA) is found in two regions of the brain, the first being in the nucleus of the hypothalamic central area and the second being in the mesencephalon (midbrain) region connecting to the front portion of the brain (see Appendix A).This area is of particular interest, as this is where dopamine neurons will regulate several aspects of human function i.e. motor function, memory and behaviours. These dopamine neurons are responsible for many of the learned behaviours throughout life (Girault & Greengard, 2004). Dopamine is also found in peripheral tissues, such as the kidneys and lungs and has been known to aid in regulation of sodium levels and electrolyte function (Drozak & Bryla, 2005).
Dopamine has been strongly allied with reward-seeking and gratifying behaviours. The release of dopamine into the body causes an endorphin like reaction which causes individuals to express the desire to seek risky behaviours which can lead to a repetitive lifestyle e.g. drug taking, sexual addiction and gambling. A dangerous decrease in dopamine levels has been linked to mental psychosis, schizophrenia, depression and anxiety (Ferguson & Beaver, 2009). Polymorphisms found in negative dopamine production have also been closely linked to disorders such as Attention Deficit Hyperactivity Disorder (ADHD), Huntington’s disease and autism. Even though individuals with these conditions may sometimes express violent and aggressive behaviours, several studies have argued there is little evidence to suggest individuals with decreased dopamine levels display violent/homicidal behaviours (Qadeer et al., 2017).
On the other hand, there have been a number of a studies which argue the opposite. In a study conducted by Couppis & Kennedy, 2008 dopamine functioning was manipulated in mice, which produced great bouts of aggression in the mice (Couppis & Kennedy, 2008). Aggression itself can be linked with reward-seeking behaviour, particularly in the retaliatory sense of aggression which would cause a rush of endorphins and an increase in dopaminergic activity due to the sensation of engaging in sudden violence leading to greater aggression (Chester et al., 2015). This is further highlighted through Blum’s understanding of the reward deficiency hypothesis in which persons may experience gratification from seeking environmental rewards to satisfy internal desires (Blum et al., 2000)
