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.
Identify the symptoms of the disorder represented in figure.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → The short statured individual has broad palm with characteristic palm crease.
Option (1) There is formation of abnormal haemoglobin in the individual. — Incorrect. Abnormal haemoglobin is the mark of sickle-cell anaemia, a Mendelian (single-gene) disorder. The figure shows Down’s syndrome, a chromosomal disorder, which does not change haemoglobin.
Option (2) The individual shows gynaecomastia. — Incorrect. Gynaecomastia (breast development in males) is seen in Klinefelter’s syndrome, caused by an extra X chromosome (XXY). It is not a feature of Down’s syndrome.
Option (3) The short statured individual has broad palm with characteristic palm crease. — Correct. Short stature and a broad palm with a characteristic crease mark Down’s syndrome.
Option (4) The affected individual has elongated sickle like RBCs. — Incorrect. Elongated sickle-like RBCs are seen in sickle-cell anaemia, where glutamic acid is replaced by valine in the β-globin chain. Down’s syndrome does not affect the shape of RBCs.
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.”
