Focus question: To what extent is gender determined by gonosomes?
I researched what factors contribute to determine gender in humans, and specifically how much gender is specified by the sex chromosomes. In addition to this, I also looked at what the effect on gender is if someone has a gonadal, gonosomal or hormonal disorder or abnormality, and to what degree gender is influenced by what an individual identifies as. I had wanted to study a topic that had a clear scientific basis, that would be possible to find appropriate sources about and that both the scientific community and non-science writers would have varying opinions on.
This topic has fulfilled all the above requirements: the research included human anatomy, genetics, and sex differentiation in humans; it was possible to find current scientific literature (in book and website form) as well as older books that help to show changes in accepted science; and I could also use the writing of an activist who is more focused on the sociological and psychological than the scientific.
Review of Literature
This book takes a very clear, simple view on what determines gender in humans. If an ovum is fertilised by a sperm carrying 'an X cell...the result will be a girl'. An ovum fertilised by a sperm carrying 'a Y cell...will produce a girl'. According to Kaluger, sex is only determined by gonosomes, and the only two possible combinations are XX and XY. There is no mention of people with hormonal or gonosomal disorders, and the book therefore provides no explanation as to what decides the gender of someone who is, for example, XYY.
In Chapter 8, under the sub-heading Sex roles, there is an acknowledgement that gender is also 'sociological and psychological' . People who were previously termed hermaphrodite but are now more commonly called intersex are born with genitals of ambiguous gender, and tend to exhibit both male and female physical characteristics at puberty. In a situation like that, it would be more useful to determine the person's gender in terms of their psychological and sociological state, and not their physical one.
Guttman et al. also believe that 'X-bearing sperm' produce 'a female XX zygote', while a 'Y-bearing sperm' will produce 'a male XY zygote' . However, they place the emphasis on the presence of a Y chromosome, and state that 'a zygote with a Y chromosome develops into a male while a zygote without one becomes a female.' One of the few known genes on the Y chromosome is SRY, which causes gonads to develop into testes instead of ovaries.
In Chapter 5, under the sub-headings Nondisjunction of chromosomes and XYY males: a genetic dilemma, there is an exploration of the issue of people with 'unusual numbers of sex chromosomes [and] gonadal dysgenesis and other unusual sexual characteristics' . The first of these is XXY or Klinefelter syndrome. Boys with this disorder have gynecomastia (unusually large breast development in males),...