question_answer

Directions : (46 - 50)

Read the passage given below and answer the following questions.

The chromosomal disorders on the other hand 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 (hyper or hypo). For example. Down's syndrome results in the gain of extra copy of chromosome 21. Similarly, Turner's syndrome results due to loss of an X chromosome in human females. Failure of cytokinesis after telophase stage of cell division results in an increase in a whole set of chromosomes in an organism and, this phenomenon is known as polyploidy. This condition is often seen in plants. The total number of chromosomes of a normal human being is 46 (23 pairs). Out of these 22 pairs are autosomes or body chromosome and one pair of chromosomes are sex chromosome allosome. Sometimes, though rarely, either an additional copy of a chromosome may be included in an individual or an individual may lack one of any one pair of chromosomes. These situations are known as trisomy \[\left( 2n+1 \right)\] or monosomy \[\left( 2n-1 \right)\]of a chromosome, respectively. Such a situation leads to very serious consequence in the individual.

Trisomy is :

A) One chromosome less than 2n

B) One chromosome more than 2n

C) A hybrid obtained by crossing diploid and tetraploid

D) Three chromosomes more than 2n