Genetics Neet Crash Course Biology | Sex Determination

In this videos we are going to Sex determination in genetics refers to the biological system that establishes an organism's sex based on genetic, chromosomal, or environmental factors. Here are the key genetic mechanisms of sex determination:

1. Chromosomal Sex Determination

XX-XY System (e.g., Humans, Most Mammals)

Females: XX

Males: XY (The Y chromosome carries the SRY gene, which triggers male development.)


ZZ-ZW System (e.g., Birds, Some Reptiles, Butterflies)

Females: ZW

Males: ZZ


XX-XO System (e.g., Some Insects like Grasshoppers)

Females: XX

Males: XO (Only one X chromosome, no Y)



2. Genetic Sex Determination (GSD)

In some species, specific genes (rather than whole chromosomes) determine sex.

Example: The DMRT1 gene in birds plays a role similar to the SRY gene in mammals.


3. Environmental Sex Determination (ESD)

Temperature-dependent Sex Determination (TSD): In reptiles like turtles and crocodiles, incubation temperature influences sex.

Social Sex Determination: Some fish, like clownfish, can change sex based on social hierarchy.


4. Haplodiploidy (e.g., Bees, Ants, Wasps)

Females: Diploid (develop from fertilized eggs).

Males: Haploid (develop from unfertilized eggs).


Sex determination is complex and can involve combinations of genetic and environmental factors. Do you need details on a specific organism or mechanism?

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