Normal and Abnormal Sexual Development Flashcards
_________ gene regulates the inactivation of one X chromosome in female
XIST
what are the four levels of sexual differentiation?
chromosomal
gonadal
internal sexual organs
external genitalia
what does the “silenced” X chromosome become?
Barr body
what is one gene involved in gonadal differentiation located on autosomal chromosomes?
steroidogenic factor-1 (SF-1)
what autosomal genes lead to development of sertoli cells?
SOX-9
repressor element
what does the gene Wnt-4 do?
suppresses leydig cell development
paramesonephric duct development
what activates the steroidogenic enzymes necessary to synthesize testosterone?
steroidogenic factor-1 (SF-1)
what leads to development of male external genitalia?
5alpha-dihydrotestosterone (5alpha-DHT)
_________________ is converted to 5alpha-dihydrotestosterone
testosterone
what converts testosterone into 5alpha-dihydrotestosterone?
5alpha-reductase
what is 5alpha-dihydrotestosterone needed for development of?
prostate
bulbourethral glands
penis
scrotum
does the primordial contain 5alpha-reductase in both the male and female embryo?
yes
what is testosterone converted into in the brain?
estradiol by aromatase
what is intersex?
an animal with characteristics of both sexes: chromosomal, hormonal, and/or internal organ/external genitalia level
what are the three main categories of disorder of sexual development?
sex chromosome disorder of sexual development
XX disorder of sexual development
XY disorder of sexual development
what is a chimera?
animal that is a mix of two genetically distinct cells that originated from different embryos
what is a mosaic?
animal that contains two or more genetically different cells
what is a true hermaphrodite?
gonadal tissue of both sexes present
what are some conditions associated with chromosomal anomalies?
XO gonadal dysgenesis of horses
seminiferous tubular dysgenesis
freemartin- chimerism in cattle
what are some features of XO gonadal dysgenesis of horses?
similar to turner’s syndrome in humans
small height and weight
sterile, not estrous cycle
streak gonads
what are some signs of seminiferous tubular dysgenesis (similar to kleinfelter’s in humans) (XXY)?
atrophic testes
lack of secondary male characteristics
infertility associated with the absence of striking reduction in sperm
lower than normal serum testosterone
what is a male calico cat almost always?
XXY
what type of chimeras are freemartins?
hematopoietic
what is the freemartin effect caused by?
testicular tissue forming in the female ovary: AMH/MIS and androgens
what are some traits of freemartins?
shortened/incomplete vagina
formation of vesicular glands
hypoplastic gonads/streak gonads
hypoplastic vulva
enlarged clitoris
what are some types of gonadal dysgenesis?
gonadal hypoplasia
XY gonadal dysgenesis
gonadal dysgenesis related to chromosomal anomalies- sex chromosome DSD
what type of gene is swedish highland breed ovarian hypoplasia?
autosomal recessive gene
what is the phenotypic appearance in XY gonadal dysgenesis?
appear to be females
what are the ovaries like in XY gonadal dysgenesis?
small with no, or reduced numbers of ova
often streak ovaries
what are some ways that gonadal sex differs from internal reproductive organ and/or external genitalia sexual development?
XX sex reversal
androgen insensitivity
persistent mullerian duct syndrome of miniature schnauzers
drug induced intersexuality
what happens in XX sex reversal with the genes?
XX, but SRY/TDF (or other male associated fertility gene) is located on paternal X or on autosome
what is the Y effect gene (recessive) in the polled goat intersex associated with?
polled gene (dominant)
what is the problem in females with polled goat intersex?
variably masculinized
are individuals with androgen insensitivity XY or XX?
XY
describe the phenotype of individuals with androgen insensitivity (XY DSD)
testes in abdomen
male internal reproductive organs
external phenotype is female
what are testosterone levels like in androgen insensivity?
high
what is the etiology of androgen insensitivity?
deficiency of androgen receptors
what are individuals with persistent mullerian duct syndrome of miniature schnauzers phenotypically?
male
what sex organs do individuals with persistent mullerian duct syndrome of miniature schnauzers have?
cryptorchid testes
uterus
what might XY pseudohermaphrodite syndrome (persistent mullerian duct syndrome) of miniature schnauzers be due to?
lack of AMH/MIF
when can problems develop with drug induced intersexuality (XX DSD or XY DSD)?
pregnant animals administered hormones (testosterone, estrogen) or substances that act like these hormones
when diagnosing DSD, what should you determine?
if the problem is at the level of the sex chromosomes, gonads, internal reproductive organs, or external genitalia
what does steroidogenic factor-1 control?
gonadal differentiation
androgen production
anti-mullerian hormone/mullerian inhibiting substance production
what does Wnt-4 support the development of?
paramesonephric duct
what does sexual behavior depend on?
hormonally driven development of appropriate areas of the brain during gestation
what do XO gonadal dysgenesis of horses, seminiferous tubular dysgenesis, and freemartins all have?
gonadal dysgenesis
what is the karyotype of freemartins?
60XX
60XY
what is XY gonadal dysgenesis phenotypically similar to in people?
complete androgen insensitivity syndrome: have testes and produce testosterone
do animals with androgen insensitivity have uteruses?
no
how can you diagnose androgen insensitivity?
testosterone levels
karyotyping
what happens in congenital adrenal hyperplasia that viralizes the fetus?
gland of fetus produces excess androgen
