In humans, which of the following is a primary determinant of maleness...
In humans, the presence of a Y chromosome results in formation of testis. If the Y chromosome is absent, then ovaries are formed.
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In humans, which of the following is a primary determinant of maleness...
Presence of a Y chromosome
The primary determinant of maleness in humans is the presence of a Y chromosome. The Y chromosome is one of the two sex chromosomes, with the other being the X chromosome. While females have two X chromosomes (XX), males have one X and one Y chromosome (XY). The presence of the Y chromosome triggers the development of male characteristics during embryonic development.
Role of the Y chromosome
The Y chromosome carries a gene called SRY (sex-determining region Y), which is responsible for initiating the development of male sex characteristics. SRY activates a cascade of genetic events that lead to the production of male hormones, specifically testosterone. Testosterone is crucial for the development of male reproductive organs, such as the testes, as well as secondary sexual characteristics like facial hair, deepening of the voice, and muscle development.
Inheritance of sex chromosomes
The sex chromosomes are inherited from the parents, with the mother always contributing an X chromosome and the father contributing either an X or a Y chromosome. If the sperm carrying an X chromosome fertilizes the egg, the resulting offspring will be female (XX). If the sperm carrying a Y chromosome fertilizes the egg, the resulting offspring will be male (XY).
Exceptions to the rule
While the presence of a Y chromosome is the primary determinant of maleness, there are rare genetic conditions that can result in individuals with atypical sex chromosome combinations. For example, individuals with Androgen Insensitivity Syndrome (AIS) may have an XY genotype but develop female physical characteristics due to the inability of their bodies to respond to androgens (male hormones).
Conclusion
In conclusion, the primary determinant of maleness in humans is the presence of a Y chromosome. The Y chromosome carries the SRY gene, which triggers the development of male sex characteristics during embryonic development. While exceptions to this rule exist, the overwhelming majority of males have an XY genotype.