Question

In human karyotype, how many pairs of chromosomes have secondary constriction and satellite?

• A. 3
• B. 4
• C. 2
• D. 5

Answer 1

The correct option is D 5

Secondary constriction can be found at a chromosome in addition to primary constriction/centromere. Chromosomes can bend only at the site of primary constriction during Anaphase. Secondary constrictions are useful in identifying a chromosome from a set. There are either 0, 1, 2, 3, or 4 secondary constriction sites in a cell at anaphase. Some parts of these constrictions indicate sites of nucleolus formation and are called "Nucleolar Organizing Regions." The nucleolus is the nucleus remains associated with NOR region of secondary constriction area. In human, the number of NOR is equal to the number of nucleoli. In human, the number of NOR is 10. NOR occurs in SAT (satellite chromosome) chromosomes (13,14,15,21,22).

So, the correct answer is '5'.