Principles of Inheritance and Variation Test - 13

In human beings, a pair of X chromosome is found in female and presence of an X and Y chromosome are determinant of male characteristic.

In grasshopper, sex determination is of XO type, in which the males have only one X-chromosome besides the autosomes whereas females have a pair of X-chromosome.

Hemophilia is sex-linked recessive disease due to mutation in X-chromosome. In this disease blood clotting do not takes place in case of injury and minor cut leads to death of individual.

Female heterogamety is the formation of different types of gametes in female. Although male produce same types of gametes. In birds the female have ZW sex chromosome and male have ZZ sex chromosome.

Two genes located very close on the chromosomal linkage map. Segregation of R and Y will not takes place due to linkage and passes to same gamete together but overall segregation can be expected as usual as dihybrid cross, 9:3:3:1.

The specific nuclear structure in few insects and 50 percent of the sperm observed by Henking was named as X body. Although its role in sex determination was not known to his time.

Male produce two kinds of sperms, half carrying X and half carrying Y sex chromosome besides 22 autosomes. If ovum is fertilized by sperm carrying X chromosome the sex of child developed is female.

Women are not responsible for sex of child because they produce only one kind of gamete containing X-sex chromosome, on the other hand male produce two kinds of sperms half containing X and half Y sex chromosome.

Henking trace a specific structure in 50% of sperms. He gave the name x-body to this structure but he was not able to explain the significance of this structure. Further, investigation revealed that x-body was a chromosome, called X-chromosome.