Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Sex reversal
Sex reversal
The old assertion is that ovarian development was essentially a default
phenomenon that proceeded in the absence of Sry and downstream genes
such as Sox9 is defunct
...
As Eicher and Washburn put it in an important report:
Some investigators have overemphasized the hypothesis that the Y chromosome is
involved in testis determination by presenting the induction of testicular tissue as an active
(gene-directed, dominant) event while presenting the induction of ovarian tissue as a
passive (automatic) event
...
Almost nothing has been
written about genes involved in the induction of ovarian tissue from the undifferentiated
gonad
...
Nevertheless, speculation on the kind of gonadal
tissue that would develop in an XX individual if ovarian tissue induction fails could provide
criteria for identifying affected individuals and thus lead to the discovery of ovariandetermination genes
...
The fact that timing is important in sex determination derives from their
insight: there are interesting data from inbred mice that demonstrate that male
sex is indeed determined by the timing of activation of the downstream SOX9
gene (set in motion by the Sry) which must act at specific times and in specific
locations in differentiation
...
’”25 Bullejos and Koopman
studied inbred XY mice in which the action of the downstream SOX9 gene was
26
delayed, producing sex reversal in the XY setting
...
27 In
humans, mutations in the SOX9 gene produce not only ambiguous genitalia but
have an impact on the skeletal system, hearing and facial features as well: the
syndrome is campomelic dysplasia; About 75% of these individuals have
ambiguous genitalia or normal female genitalia in the presence of an XY
chromosomal complement
...
reported an XY infant, a phenotypical female, (XYDSD) with
an abnormality in the nuclear receptor steroidogenic factor SF-1 (also known as
Ad4BP) that is essential for normal adrenal and gonadal development in humans
...
She responded to
follicle-stimulating hormone and luteinizing hormone but there was no
testosterone response after stimulation with human chorionic gonadotropin
...
The mutation in SF-1, then, had caused complete
sex reversal in the face of XY sex chromosomes, including normal external
female genitalia and the presence of a uterus
...
Huang et al
...
This
individual had a duplicated SOX9 gene on a rearranged chromosome 17
...
Not only does
this case present evidence that SRY is not necessary for male differentiation,
it demonstrates that a duplication of the SOX9 gene was sufficient to produce
testes differentiation in the absence of SRY