The chromosomal disorders are caused due to absence, excess or abnormal arrangement of one or more chromosomes. Failure of segregation of chromatids during cell division results in the gain or loss of chromosome(s), called aneuploidy.
The figure represents the karyotype of a person suffering from:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Down's syndrome
Option (3) Down's syndrome — Correct. The karyotype has three copies of chromosome 21 (trisomy 21). This is the cause of Down’s syndrome: short stature, small round head, furrowed tongue, partly open mouth and retarded development.
NCERT Extract:
Chromosomal Disorders – “… Down’s Syndrome : The cause of this genetic disorder is the presence of an additional copy of the chromosome number 21 (trisomy of 21). This disorder was first described by Langdon Down (1866). The affected individual is short statured with small round head, furrowed tongue and partially open mouth (Figure 4.16). Palm is broad with characteristic palm crease. Physical, psychomotor and mental development is retarded.”
