Question

Due to nondisjunction of chromosomes during spermatogenesis, sperms carry both sex chromosomes (22A + XY) and some sperms do not carry any sex chromosome (22A + O). If these sperms fertilise normal eggs (22A + X), what types of genetic disorders appear among the offsprings?
A. Turner’s syndrome or klinefelter’s syndrome
B. Down’s syndrome or klinefelter’s syndrome
C. Down’s syndrome or Turner’s syndrome
D. Down’s syndrome and cri- du –chat syndrome

Answer 1

During the cell division the failure of homologous chromosomes or sister chromatids to be separate is called nondisjunction of chromosomes. Monosomy occurs when one chromosome is lost from the diploid set(2n-1) and turner’s syndrome occurs due to monosomy.

Complete Answer:
- Monosomy occurs when union of an abnormal egg and a normal sperm occur or a normal egg and an abnormal sperm union occur. The individual has 45 chromosomes( 44+ X ) instead of 46 chromosomes.
- Basically the cause of turner’s syndrome is the absence of one of the chromosomes in females. The affected female is sterile as their ovaries are rudimentary. Lack of other secondary sexual characters in females.
- They are dwarf and mentally retarded. Small uterus, undeveloped breasts, puffy fingers, short stature, webbed neck, cardiovascular abnormalities, abnormal intelligence and hearing impairment are the features of the person affected by turner’s syndrome.
- Klinefelter’s syndrome occurs due to trisomy chromosomal disorder.
- Genetic constitution of the syndrome is the union of an abnormal XX egg and normal Y sperm or normal X egg and abnormal XY sperm. In this syndrome the individual has 47 chromosomes( 44 + XXY).
- These persons are sterile male with mental retardation, undeveloped taste, sparse body hairs like females, long limbs, knock knees, with feminine pitch voices and enlarged breasts.

So from the above explanation it is clear that option a is correct.

Note: A large number of diseases inherited from parents to the offspring. Such diseases are known as genetic disorders. Most of these diseases are caused by expression of recessive allele.