(i)How does a chromosomal disorder differ from a Mendelian disorder?
(ii) Name any two chromosomal disorders.
(iii) List the characteristics of the disorders mentioned above that help in their diagnosis.

Explanation

Mendelian disorder refers to a genetic disease showing a Mendelian pattern of inheritance, caused by alteration or mutation in the single gene But the chromosomal disorder is caused due to absence or excess or abnormal arrangement of one or more chromosomes. (1) Klinefelter's syndrome: Turner's syndrome: Down's Syndrome tu Turner's Syndrome. Turner's syndrome is due to monosomy (2n-1). It is formed by the union of an allosome free egg (22-0) and a normal X sperm or a normal egg and an allosome free sperm (22-0). The individual has 2n = 45 chromosomes (44 +XO) instead of 46. Such persons are sterile females who have rudimentary ovaries. filled with connective tissue, undeveloped breasts, small uterus, puity fingers peripheral lymphoedema), short stature less than 5 feet), webbed neck and abnormal intelligence, cardiovascular abnormalities and hearing impairment. They may not menstruate or ovulate. 44 +YO combination for male Turner's syndrome) is unviable so that it does not occur in nature Klinefelter's Syndrome. Klinefelter's syndrome is due to trisomy of sex (X) chromosome. It is formed by the union of an abnormal XX egg and a normal Y sperm or normal X egg and abnormal XY sperm. The individual has 47 chromosomes (44+XXY). Such persons are sterile males called feminised male) with undeveloped testes, mental retardation, female like sparse body hair, and knock knees, long limbs and with some female characteristics such as feminine pitched voice and enlarged breasts gynaecomastia), It is considered that the more the X chromosomes the greater is the mental defect