Genetically Controlled Sex Determining Mechanism

In many organisms, including humans, sex is determined by specific genetic mechanisms. There are two primary mechanisms for genetically controlled sex determination:

1. XX-XY System (Gonadal Sex Determination):

In this system, sex is determined by the presence or absence of specific sex chromosomes.

In humans and many mammals, females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

The presence of the Y chromosome leads to the development of male reproductive structures, while the absence of the Y chromosome results in the development of female reproductive structures.

The SRY (Sex-determining Region Y) gene on the Y chromosome plays a critical role in male sex determination.

2. ZZ-ZW System (Gonadal Sex Determination):

This system is found in some animals, including birds, reptiles, and certain species of fish and insects.

In this system, males have two of the same sex chromosomes (ZZ), while females have two different sex chromosomes (ZW).

In birds, for example, males (ZZ) typically produce ZZ sperm, and females (ZW) produce both ZW eggs and WW eggs. The combination of sperm and eggs determines the sex of the offspring.

It’s important to note that the specific genetic mechanisms of sex determination can vary widely among different species. While humans and mammals use the XX-XY system, other organisms employ different systems, including environmental factors or complex genetic interactions. Additionally, some species exhibit genetic diversity in sex determination mechanisms.