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  4. Statement-I: 2A + X0 genotype represents turner syndrome in women. Statement-II: 2A + X0 genotype is normal male in grasshopper.

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Q. Statement-I: 2A + X0 genotype represents turner syndrome in women.
Statement-II: 2A + X0 genotype is normal male in grasshopper.

NTA AbhyasNTA Abhyas 2020Principles of Inheritance and Variation

Solution:

XO type (XX-XO type): It is observed in large number of insects, grasshopper. Numbers of chromosomes are different in male and female individuals. Here, female shows homogameity (XX) while male shows hetrogameity (XO). It is clear that, all eggs (ova) bear an additional X-chromosome besides the autosomes while only 50% of the sperms bear X-chromosomes. In grasshopper, eggs fertilized by (A+X) type sperm become females while those fertilized by (A+O) type sperm become males. Therefore, sperm determines the sex of the offsprings.
TURNER’s SYNDROME:
Introduction: It was first described in 1938 by Turner. The disorder develops due to monosomy of sex chromosome. The disease is seen only in females. It is an allosomal chromosomal abnormality.
Cause: The disorder is due to monosomy. It appears due to fusion of abnormal egg (22+0) and a normal sperm (22+X) or a normal egg (22+X) and abnormal sperm (22+0).
Karyotype: [44 + XO]