Final answer:
The statement is true; the presence of the Y chromosome is crucial in determining male sex due to the SRY gene initiating male development, which contrasts with the default development into female in its absence.
Step-by-step explanation:
Role of the Y Chromosome in Determining Male Sex
The presence of the Y chromosome is indeed a key factor in determining male sex. This statement is true. The Y chromosome contains several genes associated with male development, with the most critical being the SRY gene (Sex-determining Region Y gene). The SRY gene initiates the development of a male by setting off a series of events that stimulate the formation of testes and the production of testosterone, leading to the development of male sexual organs. Absence of the Y chromosome typically results in the development of female reproductive characteristics since the embryo does not receive the SRY signal to develop as a male.
Regarding the size of the Y chromosome compared to the X chromosome, it is significantly smaller because it carries fewer genes. The X chromosome has approximately 2,000 genes, while the Y chromosome has less than 100. However, when it comes to determining sex, the Y chromosome's genes have a crucial role, despite their small number. The size difference may be attributed to evolutionary processes where non-essential genes are lost over time, and the Y chromosome has retained only those critical for male development.
It's important to understand that while mothers can only pass on an X chromosome, fathers can pass on either an X or a Y chromosome, thus determining the sex of the offspring. A sperm carrying a Y chromosome will result in a male (XY) child, while a sperm carrying an X chromosome will result in a female (XX) child.