Question

A woman with $47$ chromosomes due to three copies of chromosome $21$ is characterized by

• A. Down syndrome
• B. triploidy
• C. Turner syndrome
• D. super femaleness

Answer 1

Answer: (A)

Down's syndrome is due to an extra chromosome, which combines to the chromosome pair $21$. Down syndrome is caused due to trisomy, in which the fusion of a normal $n$ gamete (haploid) takes place with an $n+1$ gamete (diploid). J. Langdon Down first described the developmental defect produced by trisomy in $1866$ . For this reason it is called Down's syndrome. Persons having Down's syndrome generally have a short, stocky build short hands, flattened facial features and poor muscle tone. In addition they are mentally retarded.