A personality is a mixture of traits that define ones individual personality. Examples of this include, impulsiveness, openness, intelligence, etc. These traits are tools, which are used by individuals to navigate social situations. Dr. Dean Hamer is a molecular psychologist and he is exploring the roll that genes play in a human personality. He said until recently, research into behavior genetics was based on a study of identical twins. This study was based on the idea that if one of the twins turned out to be homosexual then there is a 50% chance that the other one will be as well.
That study was conducted b psychologist Michael Bailey of Northern University). Hamers research picked up where that study left off which on exact sections of DNA that influence behavior. Copeland, 1993 In the first part of research of Hamers into behavioral genetics created quite a controversial when published journal Science 1993 because Hamer and his research team determined that homosexuality appeared to be linked to a stretch of DNA at the very tip of the X chromosome men inherit from their mothers. Three years later, in 1996, Hamer and his collaborators at HIH seconded an Israeli group.
They found a link to a gene on chromosome 11 to the personality trait psychologists call novelty seeking. That same year Hamers’ lab helped pinpoint another gene, this on chromosome 17 that appears to play a role in regulating anxiety. Copeland, 1993 These kinds of genes are not the kinds that cause people to be homosexual. The chemical balancing of a person is much more intricate than that, what genes seem to do, is subtly bias the psyche so that different individuals react to similar experiences in surprisingly different ways. Copeland, 1993
Other scientists question these results because no other research team has been able to replicate Hamers work results. Possible there s no link between these genes and personality traits. On the other hand, they re maybe an even better explanation. Dr. Dennis Murphy of the National Institute of Mental Heath Suggests that a simple trait acidity is not controlled by a simple gene of a tomato it takes as many as 30, this he speculates maybe the way humans act in a given circumstance. To argue the biological part of this, It is known that those who are mal-adaptive, or don t produce in other words, don t survive.
Now, if that were true homosexuals would have been weeded out long ago. Strait Science? McKnight, Jim PG 19 Biological Accounts The oldest explanation to homosexuality is; Homosexuality is an interruption of normal heterosexual development. The old theory was that Homosexuality was basically a birth affect. And now resent research, has tried to discover a genetic basis for homosexuality, which will expect it as a normal variability Scientists say that if it keeps happening over and over then there must be a purpose. Strait Science?
McKnight, Jim PG 22 Homosexuality is beloved to be a couple of different things such as, chemical imbalances, birth affect, or perverted experimentations. Another interesting point to this is At conception we re all female but, by the end of the first trimester of pregnancy those who will be male are exposed to small doses of two triggering hormones, Choriconic gonadotropin and luieinising hormone. These are secreted by our mothers pituitary gland and enter her blood stream, cross the placenta and start the differentiation of gonads into testes.
The rapidly developing testes then take over the job of continuing male differentiation and secrete male sex hormones. Strait Science? McKnight, Jim PG 22 The brain is a sexual organ and part of the differentiation into maleness is an appropriate androgenisation of the brain. Yet unlike other gross sexual characteristics, androgenisation of the brain does not require defeminisation of the basic female pathways. Whereas the undifferentiated gonad becomes either a testis or an ovary, in the brain differentiation seems to lay down independent pathways towards maleness and femaleness.
Thus, acquiring masculine brain characteristics, and at different times Goy and McEwen, 1980 and involve quite different neural substrates as well as different hormonal metabolites Byne and Parsons, 1993. Homosexuality is seen as an interruption of this process, an altering of the relative balance between the two systems, leading to a change in the sexual orientation, which is at odds with one s genetic predisposition Jim McKnight, 1997. One example of sexual inversion is 5-alpha reductase deficiency.
Julianne Imerato-McGinley and her colleagues in 1974 reported a pool of natural transsexuals who started life as girls but later became boys. For at least three generations several families in the central Dominican Republic have had sufficient numbers of girls turns into boys to suspend a final gender assignment until puberty settles the matter Imperato-McGinley et al. , 1974 1979. These guevedoces, (eggs (testes) at 12) children, are born with female genitalia. At puberty, under the influence of testosterone, some girls make a complete transformation to boys, developing full male genitalia.
For others the physical changes are less complete with only partial fusion of the vagina, requiring reconstructive surgery. While the incidence of 5-alpha reductase deficiency seems concentrated in these Dominican villages, it has been noted in many other communities e. g. Money and Ehrharde, 1972. The process is relatively straightforward even if the causes are still obscure. It appears an autosomal fenetic deficiency inactivates the enzyme 5-alpha reductase, which is normally converts testosterone into dihydrotestosterone (DHT).
DHT, which is present in both genetic sexes, has a primary role in masculinising male external genitalia Savage et al. , 1980. Genenetic males who have this deficiency produce normal amounts of testosterone but this is not converted into DHT and the child s genitals develop according to our species female default. While this is a clear case of sexual inversion, it does not model homosexuality, or at least not a recognizable male homosexuality. As a natural experiment, it fails to be convincing as this culture has a high tolerance of sexual ambiguity but nevertheless does assign a gender at birth Breedlove, 1994.
If the child s gender assignment is female, they might be considered lesbians, as, at puberty, these children prefer female sex partners, irrespective of complete their subsequent masculinisation is Rubin et al. , 1981. However, if their assignment is masculine of intermediate (raised as girls waiting to become boys) they have quite clear masculine identity and heterosexual orientation at puberty Breedlove, 1994. What is important in this research is the question of desire. These children, first raised as either girls or boys or an intermediate, desire women and this is unlikely to change even if their gender does.
One explanation of such results is that: fetal testosterone masculinzed to brain so that, social rearing notwithstanding, the individuals were inclined to think and therefore behave like men Breedlove, 1994. That they favor other women and that this is a fixed inclination regardless of gender reassignment suggest other than a learned role for sexual direction. Darwin s theory states that genetic material (DNA) can pass in its original state from generation to another. However, occasionally, there is a permanent change in the DNA message and this is called mutation.
The chromosomes in the sperm (26) and in the egg (26) are combined in the fetus to total 46. These chromosomes from each parent are random and are the inherited traits in the child. Lamarck s Signature, Steele, Robyn, and Blander During the past 40 years, more than a dozen twin studies of male sexual orientation have been described, and the pattern is the same. The genetically identical twin of a gay man has a greatly increased chance- though not a 100 percent chance of also being gay, which is higher than the rate for fraternal twins, which is still higher than the rate for unrelated people.
This is just the pattern expected for a trait that is influenced- but not strictly determined by-genes. Averaging all the studies to date, the heritability of male sexual orientation is about 50 percent genetic and 50 percent from other influences, a ratio found in many other behavioral traits. Hamer, 1998 In research on homosexuality, subjects were determined by using the Alfred Kinsey Scale this is a scale from 0 for exclusive heterosexuality, to 6 for exclusive homosexuality. The numbers in between represent degrees of bisexuality and fantasy. The interesting this was the difference in scores for men and women.
Men almost always were either, heterosexual or homosexual, and very rarely bisexual. Women however, tended to range completely across the scale. Research seems to indicate that women were more influenced by environment such as their sister or their mother being lesbian. Men, who are homosexual, had mothers that had relatives that were homosexual. In other words, the gay men had gay relatives on their mothers side. In the case of twin men, raised by the same parents in the same home, it was indicated that parenting style made no difference in sexual preference.
Because males always receive their X chromosome from their mother, any gene on the X chromosome is passed through the mother. Indeed, the pattern of male homosexuality looked similar to the patterns for color blindness or hemophilia, two classic X-linked traits. The inheritance was less strong tan for a purely genetic trait, but that wasn t surprising because sexuality is so complex that there were likely to be multiple genes and strong environmental factors. There is no way that the father can pass the X-chromosome to his son. Linkage was found in a region called Xq28, located on the very tip of the long arm on the X-chromosome.
In that region, 33 out of the 40 pairs were the same. These results were found and only one experiment of a particular population of gay men and then, another study testing DNA of gay men to see if there was any excess marker sharing in the Xq28 region. This time there was a 67% shared markers. On a third study Hamer and his crew studied heterosexual brothers of gay men. This time most of the strait men had different markers from their gay brothers. Our statistical experts estimated that the degree of DNA sharing of the straight brothers with their gay brothers was 22 percent, significantly lower than the 50 percent expected by chance.
This independent confirmation that Xq28 was involved in sexual orientation-straight as well as gay. The evidence is compelling that there is some gene or genes at Xq28 related to male sexual orientation. What still is needed is corroboration from other laboratories. That hasn t happened yet, and the progress is depressingly slow. Four years after our results were published, no other group has published a single scientific manuscript on this topic. If we had discovered a gene for something less controversial, say diabetes or schizophrenia, scientists would have been fighting to replicate it, or shoot it down.