What Happens in the Presence/Absence of SRY

[GingerBread27]

I'm confused as to what happens when the SRY gene is not present. In the book I use it says the gonads will become ovaries,but in my class notes it says testes will form. Can someone please explain to me SRY and what it relates to? Thanks

 

[Moonbear]

SRY is present on the Y chromosome and is responsible for regulating a cascade of other genes required for differentiation of the primordial gonads into testes. In case studies in which individuals with an XY karyotype had a mutation of the SRY gene, they developed into phenotypic females, but had what are referred to as streak gonads, not ovaries. (i.e., Jager RJ, Anvret M, Hall K, Scherer G. A human XY female with a frame shift mutation in the candidate testis-determining gene SRY.
Nature. 1990 Nov 29;348(6300):452-4.) So, while SRY is a testis determining factor, something else seems necessary as an ovary determining factor.

However, there is a current case report out of a phenotypic male with a 46XX karyotype who does not have the SRY gene and still has testicular development (though is infertile). This suggests it is not SRY itself that is involved in testicular development, but other genes it may regulate (that might be the source of the mutation in this patient).

Fertil Steril. 2005 Jan;83(1):216-9.
A 46,XX SRY-negative man with complete virilization and infertility as the main anomaly.

Valetto A, Bertini V, Rapalini E, Simi P.

OBJECTIVE: To report a case of a 46,XX SRY-negative man with a male phenotype and azoospermia. DESIGN: Case report. SETTING: Molecular and Cytogenetic Unit in a University Hospital. PATIENT(S): A 35-year-old man with complete masculinization who referred to our institution because of a history of several years of infertility. INTERVENTION(S): Lymphocytic karyotype and genetic counseling. MAIN OUTCOME MEASURE(S): Peripheral blood metaphases were analyzed by standard G-banding and Q-banding. Fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) analyses were performed. RESULT(S): Semen analysis showed azoospermia. Chromosome analysis revealed a 46,XX karyotype; molecular and cytogenetic analyses excluded the presence of SRY (the sex-determining region of the Y chromosome) gene. CONCLUSION(S): This case is one of the rare patients reported in the literature in whom testicular differentiation and a complete virilization in a 46,XX chromosomal constitution does not account for a translocation of the SRY gene to the X chromosome or to the autosomes. This finding suggests that other genes downstream from SRY, not yet identified, play an important role in sex determination.

Edit: I realize I didn't define a streak gonad for you.

streak gonads, **undeveloped gonadal structures found in the broad ligament below the fallopian tube and composed of whorled connective-tissue stroma with no germinal or secretory cells; seen most often in Turner's syndrome.

From: here.

 

[ravenprp]

The SRY gene, also known as the sex-determining region Y, is a gene located on the Y chromosome in humans. This gene plays a crucial role in determining the sex of an individual, specifically in the development of male characteristics.

In the presence of the SRY gene, the gonads (the reproductive organs) will develop into testes. These testes will then produce testosterone, which is responsible for the development of male reproductive organs, secondary sex characteristics, and overall male physiology.

On the other hand, in the absence of the SRY gene, the gonads will develop into ovaries. Without the presence of testosterone, the individual will develop female reproductive organs, secondary sex characteristics, and overall female physiology.

The SRY gene is crucial in the determination of sex and its absence can lead to a mismatch between the genetic sex (XX or XY) and the physical sex of an individual. This can result in conditions such as Swyer syndrome, where individuals with XY chromosomes develop female reproductive organs, or complete androgen insensitivity syndrome, where individuals with XY chromosomes develop female external genitalia.

It's important to note that the development of sex characteristics is a complex process influenced by various genetic and environmental factors, and the presence or absence of the SRY gene is just one aspect of it. I hope this helps clarify the role of the SRY gene in sex determination.