Sex Determination- Lecture 1 Flashcards
Mesonephros
Embryonic kidneys. Serve as a excretory organ during gestation. Drained by a duct system: mesonephric ducts (wolffian ducts)
Genital swelling
like the genital tubercle it will develop into a scrotum or vulva depending on the presence or absence of androgens (testosterone or DHT)
Intersex
any situation where there is ambiguity in the structure of the external genitalia, internal genitalia, or gonads
Genital tubercle
Is a bipotential structure. In the presence of DHT or testosterone the tubercle develops into a penis. In the absence of those hormones the tubercle develops into a clitoris.
Gonadal dysgenesis
gonads fail to differentiate and remain in embryonic form, termed “streak” gonads
Paramesonephric/ Mullerian ducts
Tubular system developing at same time at mesonephros. Will later form the oviducts, uterus, cervix, and cranial vagina in females, or regresses in males.
Haploid
number of chromosomes in the gamete (N)
Gonadal sex
Testis or Ovary Determined by presence or absence of SRY (Sex-determining region of Y chromosome) gene of Y chromosome
Male pseudohermaphrodite
XY with testes but has female or ambiguous external genitalia
Female pseudohermaphrodite
XX with ovaries and male or ambiguous external genitalia
Sry
Sex-determining region on the Y chromosome. Produces a protein called HY antigen (Sry protein), which action is to initiate differentiation of the bipotential gonadal tissue into testicular tissue. Other genes that support Sry: Sox9, Gata4, Wtl, and Sfl
XXX
Associated with female phenotype, but is abnormal. Bilateral small, inactive ovaries and a hypoplastic uterus and cervix.
Diploid
number of chromosomes in somatic cells (2N)
XXY-syndrome
Klinefelter’s syndrome Due to presence of Y chromosome and consequently the Sry gene the individuals are phenotypically male although abnormally so. Small, flaccid testes (or retained) and azoospermia. Patient will have normal libido and behavior but often infertile.
XX sex-reversed male
can be Sry positive or negative. If positive the individual has a translocated copy of Sry, which drives gonadal differentiation in the male direction. If Sry negative, they likely have mutations in genes downstream of Sry.
Bipotential gonads
Gonad is undifferentiated. Both the male and female tubular systems are present. Sex of embryo cannot yet be determined
Differentiation of ovaries (from gonadal cords)
Gonadal cords break apart into small clusters to form follicles, with one or more germ cells in the center. The mesonephric duct regresses while the paramesonephric duct persists and will form oviducts, uterus, cervix, and cranial vagina.
Mesonephric/ Wolffian ducts
Will later form the epididymis, seminal vesicles and ductus deferens in males, or regresses in females
Mosaics and Chimeras
are animals that have than one genetically-distinct population of cells. In mosaics, the different cell types all arise from a single zygote. Results from non-disjunction during mitosis In chimeras, the different cell types originate from more than one zygote.
Aneuploidy
increase or decrease in normal chromosomal number, leading to trisomy or monosomy
Fetal leydig cells
Especially important. They produce testosterone, that is essential for normal development of male duct system, external genitalia, secondary sex characteristics and brain.
Polled intersex goats
There is a close relationship between the gene for “polled”” (hornless) and intersexuality. The polled gene is dominant autosomal. In XX patients: PP= hornless and infertile Pp= hornless and fertile pp=horned and fertile
Phenotypic sex
Male or Female determined by substances produced by testis that cause either regression/maintenance of the male/female tract. These substances also regulate the development of external genitalia, secondary sex characteristics, brain development, ect
Trisomy
extra chromosome added to a homologous pair
