"Jacob’s Syndrome" – Xyy Genotype

Introduction

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, which can occur due to inaccuracies during cell division (Robinson & Jacobs, 1999). Affecting 1 in 1000 newborn males, the XXY genotype is rare and was first reported in 1961 when a male was discovered to carry this gene after fathering a child with Down Syndrome. Following this discovery, there was a surge of reporting among males between the years of 1961 and 1965, but only a minute few were actually reported to carry the gene. Conventionally, these males are very tall (over 6 feet), experience poor coordination, have high levels of testosterone, severe facial acne, and possess a very low IQ; otherwise, they appear normal.

Jacob’s Syndrome – XYY Genotype

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 karyotype and pleaded insanity, it was not considered admissible in court (Bartholamew & Sunderland, 1966; Saxe, 1970). The feature that tends to be most commonly recognized in the literature is that individuals with the XXY defect have a ‘low’ intelligence and a higher tendency to commit crime. Another feature commonly seen among these offenders is their predominant tallness; however, this alone cannot be used to explain offender behavior.

Discussion

Combined, these features can portray a causal link between offender phenotypes (Horan, 1992). This paints a frightening picture, in which males who are of taller stature and lower intelligence levels 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 behavioral problems, leading geneticists to assume these individuals will lead a life of aggression, which is not always the case but can be fairly common. Studies show that those who do display behavioral disorders tend to be unstable, have limited concern for their actions, show little emotional response, lack empathy and compassion for others, and often exhibit aggressive outbursts (Price & Whatmore, 1967).

Conclusion

Furthermore, when socioeconomic parameters are considered, the characteristics of the XYY karyotypes are much closer to those 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 behavior seen in larger populations (Götz, Johnstone & Ratcliffe, 1999). Overall, it can be argued that the majority of population data is relatively biased, with individuals displaying certain phenotypic characteristics, such as height and IQ levels, being targeted. Many studies also have failed to take into account mental instability unrelated to the karyotype, which may affect behavior outwardly but separately from the gene (Walzer, Gerald & Shah, 1978). As most criminal cases using the XYY karyotype were inadmissible in court, it seems fair to question the authenticity behind the evidence.