Question

The non genetic sex determination occurs in
A. Bonellia
B. Cow
C. Birds
D. Fruitfly

Answer 1

Non genetic sex determination is also known a environmental sex determination. It is the establishment of sexual characters either male or female in response to environmental factors like nutrient availability, temperature.

Complete Answer:
Sex determination is the determination of sexual characteristics in an organism.

Types of sex determination:
1. Genetic sex determination- It is controlled by the genes or chromosomes. In mammals, X and Y determine the female and male as in the case of cow, human etc.
2. Non-genetic sex determination- It is the establishment of sexual characteristics which is regulated by the external environment.
- For example in Bonellia- It is a unique kind of marine organism in which the egg hatch into larvae which are sexually indifferent. The ones which settle freely in the sea floor develop into females and the ones which develop attached to the female proboscis as male who are dwarfs. They remain permanently attached to the female body.
- Birds: Sex is determined by chromosomes. ZZ represents male and ZW represents females.
- Fruit fly: the sex is determined by the balance of female determinant on the X chromosome and male on the autosomes. In male there is one X chromosome in the diploid cell.

The correct answer is (A). The non genetic sex determination occurs in Bonellia.

Note: Once sex is determined, it is fixed for life time. The characteristic features of the organisms showing non-genetic sex determination are females are larger than male, sexual dimorphism, parasitism and variable sex ratio.