Introduction

Sex determination in humans hinges on the presence or absence of the Y chromosome, and more specifically the location of critical sex-determining genes on its structure. The Y chromosome consists of a short arm (p arm) and a long arm (q arm), each carrying different genetic information. Understanding which arm harbors male-determining genes is fundamental to interpreting various chromosomal disorders affecting sexual development.

Genes for Maleness on the Short Arm of Y Chromosome

• The SRY gene, key to initiating male sex determination, is located on the short arm of the Y chromosome (Yp) near its tip.

• Individuals possessing the short arm of the Y chromosome along with an X chromosome develop as males, even if they lack parts of the long arm.

• Conversely, individuals who carry the long arm but lack the short arm of the Y chromosome typically develop as females, indicating the absence of male sex-determining genes.

Clinical and Experimental Evidence

• Deletions or mutations affecting the short arm region of the Y chromosome lead to disorders such as Swyer syndrome, where an XY individual develops female characteristics due to the absence of functional SRY.

• Rare cases of XX males occur when the SRY gene translocates onto an X chromosome or autosome, further supporting the dominance of this gene in male determination.

• The long arm of the Y chromosome contains genes involved in spermatogenesis and male fertility but is not responsible for primary sex determination.

Summary

• The male-determining genes are located on the short arm of the Y chromosome.

• Presence of the short arm (with SRY) correlates with male development, regardless of the long arm.

• Absence of the short arm yields female development, even if the long arm is present.

Final Answer:
(1) Genes for maleness are located on short arm of Y chromosome