Sex Determination Mechanism – Class 12 | Chapter – 5 | Biology Short Notes Series PDF

Sex Determination Mechanism: A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes.

Sex Determination Mechanism

• Finalization of sex at the time of zygote formation is called sex determination.
• Two types of chromosomes are present in individuals – sex chromosomes (which determine the sex of individuals) and autosomes.

1. XX-XY TYPE

Seen in many insects and mammals including humans, Drosophila melanogaster. Males have X and Y chromosomes along with autosomes [A] and females have a pair of X chromosomes.

2. XX-XO TYPE

Seen in grasshopper. Males have only one X chromosomes besides autosomes and females have a pair of X chromosomes.

3. ZZ-ZW TYPE

Seen in birds, fowl and fishes. Females have one Z and one W chromosomes whereas males have a pair of Z chromosomes.

4. XX-XY TYPE

Seen in cockroaches. Females have only one Z chromosomes besides autosomes and males have a pair of Z chromosomes.

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By Team Learning Mantras