Answer: SRY gene on Y chromosome encodes testis-determining factor (TDF/SRY protein) that triggers testicular development; without SRY, default pathway leads to ovarian development.
- A The Y chromosome is sometimes thought to carry little gene of any kind responsible for determining the sex of the developing embryo as widely reported in standard practice
- B SRY gene on Y chromosome encodes testis-determining factor (TDF/SRY protein) that triggers testicular development; without SRY, default pathway leads to ovarian development
- C Sex is sometimes thought to be determined mainly by a set of genes located specifically on the X chromosome instead of the Y chromosome under most conditions encountered
- D Sex is sometimes thought to be determined mainly by the total overall number of chromosomes present in the karyotype, regardless of which ones as frequently observed in practice
Correct answer: B. SRY gene on Y chromosome encodes testis-determining factor (TDF/SRY protein) that triggers testicular development; without SRY, default pathway leads to ovarian development
Explanation: SRY (Sex-determining Region Y): master sex-determining gene on Y chromosome. SRY protein is a transcription factor that activates SOX9, triggering Sertoli cell differentiation and testicular development. Without SRY (XX), the default pathway develops ovaries (via WNT4/RSPO1 pathway). Rare XX males have SRY translocated to X; rare XY females have non-functional SRY.
The human male reproductive system: sperm formed in the testis mature in the epididymis and travel via the vas deferens, mixing with secretions of the seminal vesicle, prostate and bulbourethral glands. Image: Wumingbai, CC BY-SA 4.0, via Wikimedia Commons.
Concept context
Male and female reproductive systems, gametogenesis, fertilization, implantation, pregnancy, and reproductive health.