Chromosomal disorders are caused due to absence or excess or abnormal arrangement...
Chromosomal disorders are caused due to absence or excess or abnormal arrangement of one or more chromosomes.
Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called aneuploidy.
E.g., Down’s syndrome, Turner’s syndrome, Klinefelter’s syndrome.
a. Down’s syndrome
Down’s syndrome is caused by an extra copy of chromosome number 21 (trisomy of 21).
This disorder was first discovered by Langdon Down (1866).
Short statured with small round head.
Partially open mouth with protruding furrowed tongue.
Palm is broad with characteristic palm crease.
Physical, psychomotor and mental development is retarded.
b. Klinefelter’s syndrome
Klinefelter’s syndrome is caused by the presence of an additional copy of X-chromosomes, resulting in the karyotype of 44+XXY.
Sex of the individual is masculine but possess feminine characters.
Gynaecomastia i.e., development of breasts.
Poor beard growth and often sterile.
Feminine pitched voice
c. Turner’s syndrome
Turner’s syndrome is caused by the absence of one of the X-chromosomes. i.e., 44+XO.
Sterile female with rudimentary ovaries.
Shield shaped thorax.
Poor development of breasts.
Short stature, small uterus, puffy fingers.