Method of Sex determination in insect, Bird, Honeybee, Human

• In1891,  Henking,   while working on spermatogenesis of insect  observed  a nuclear body in some male gamete of insect.

• He stated that this nuclear body is present in 50% of insect but absent in remaining 50% of insect.

• He gave term X body for this nuclear body but he could not explain the significance of this X body.

• Biologist later on found that X body is  X chromosome which is most important in sex determination of organism.

• Different types of method of  sex determination are as follows:

XX - XO Type : 

• This type of sex determination is found in Insect like grasshopper etc.

• Male insect has XO chromosome as sex chromosome where as female insect has XX Sex Chromosome.

• Male insect form two diferent type of gamete that is X type and O type at the time of gamete formation therefore male is heterogametic.

• Female insect form only one  type of gamete that is X type at the time of gamete formation therefore female is homogametic.

• At the time of fertilization, if X type gamete of male  is fused with X type gamete of female than progeny will be female by recieving combination of chromosome XX.

• If O type gamete of male is fused with X type gamete of female than progeny will be male by recieving combination of chromosome XO.

ZZ - ZW Type : 

• This type of sex determination is found in Birds and Fish.

• Male bird has ZZ chromosome as sex chromosome where as female bird has ZW Sex Chromosome.

• Female bird form two diferent type of gamete that is Z type and W type at the time of gamete formation therefore female is heterogametic.

• In Birds, female is heterogametic and here sex is determined by female. This is unique procedure of sex determination. Generally male has capacity to determine the sex.

• Male bird form only one  type of gamete that is Z type at the time of gamete formation therefore female is homogametic.

• At the time of fertilization, if Z type gamete of female is fused with Z  type gamete of male than progeny will be male by recieving combination of chromosome ZZ.

• If W type gamete of female is fused with Z  type gamete of male than progeny will be female by recieving combination of chromosome ZW.

XX - XY Type :

• This type of sex determination is found in Human , Drosophila etc.

• Male Human has XY  sex chromosome where as female  has XX Sex Chromosome.

• Male human form two diferent type of gamete that is X type and Y type at the time of gamete formation therefore male is heterogametic.

• Female  form only one  type of gamete that is X type at the time of gamete formation therefore female is homogametic.

• At the time of fertilization, if X type gamete of male  is fused with X type gamete of female than progeny will be female by recieving combination of chromosome XX.

• If Y type gamete of male is fused with X type gamete of female than progeny will be male by recieving combination of chromosome XY.

Sex Determination in Honey bee or Parthenogenesis or Haplodiploid sex determination : 

Honey bee  colony has Drone, worker and Queen. Out of these ,  the development of Queen  is different fro the others.

Queen 

It is a female honey bee and develop as queen with the special reproductive organs.

This female bee  feed royal jellies during its larval stage.

It has diploid  thirty two  chromosome. It produces gamete by meiosis  during gametogenesis and it's  each gamete   also contain  sixteen chromosome.

Drones : It is male and develop from unfertilized egg of female. It has haploid sixteen chromosome. It produces gamete by mitosis during gametogenesis and each gamete  contain  sixteen chromosome.

Worker : It is sterile female and develop by the fusion of  male  female gamete . 

Sex determination in honey bee : During the fertilization, Worker or queen or  female is produced after the fusion of gamete of drone   and female gamete of queen.

Unfertilized gamete of queen  is directly developed into Drone. The development of drones from unfertilized egg is called Parthenogenesis.