Class 12 NEET Biology Principles of Inheritance and Variation Questions Part 2

Down's syndrome is caused by the presence of an extra chromosome number 21. Both the chromosomes of the pair 21 pass into a single egg. Thus, the egg possesses 24 chromosomes instead of 23 and offspring has 47 chromosomes (45+XY in males, 45+XX in males instead of 46. Turner's syndrome is formed by the union of an abnormal 0 egg and a normal X sperm or a normal egg and an abnormal 0 sperm. The individual has 45 chromosomes (44+X) instead of 46. Female with more than two X chromosomes is called superfemale. Triploidy is a condition in which an organism has three times (3n) the haploid number (n) of chromosomes.