Question

Which of these traits is not linked with Down syndrome?
A. Oily skin
B. Hypotonicity
C. Simian crease
D. Brachycephaly

Answer 1

Hint: Down syndrome, a genetic disorder is due to changes in the chromosomal arrangement which leads to various mental and physical disabilities. Down syndrome is caused due to trisomy of chromosome 21 ( an additional copy of chromosome 21 is present in an individual). It is named after the physician Langdon Down who first described this disorder.

Complete Step by Step Answer:
Down syndrome is caused due a phenomenon called nondisjunction in which during meiotic division, the chromosomes are not able to separate and give rise to cells with unequal number of chromosomes. A person suffering from down syndrome has certain easily identifiable characteristics. Hypotonicity is the decreased muscle tone and is easily observable in infants. Hypotonicity reduces as they grow older. In a normal person, even when our muscles are relaxed, there is some amount of contraction in the muscles that provides them with resistance to passive movement but an infant suffering from down syndrome appears to be like a "rag doll" because of hypotonicity as their arms and legs hang by their sides and they have very little or no control over head movement. Down syndrome has a characteristic palm crease (the older name for palm crease is simian crease). In a normal person, there are 2 palm creases but in a person suffering from down syndrome they have only one crease. The term brachycephaly is the condition where the back of the head is flattened which causes the head to widen and the forehead bulges out. This feature is also easily identifiable in down syndrome. Having oily skin is not a characteristic feature of down syndrome instead oily skin occurs when sebaceous glands make too much sebum which results in oily skin, acne and clogged pores.

Thus, the correct answer is option A:- Oily skin.


Note: There are two types of down syndrome:- Trisomy of chromosome 21 and Mosaicism. The trisomy is due to the nondisjunction of chromosome 21 during gamete formation and Mosaicism is due to nondisjunction during mitosis in the zygote.