Question

Trisomy 21 is
A. Down’s syndrome
B. Klinefelter’s syndrome
C. XYY
D. Triple X

Answer 1

Hint: Trisomy refers to a genetic condition in which a person has three copies of chromosome instead of two copies of Chromosome. Chromosome is a thread-like structure which contains proteins and DNA (hereditary material).

Complete Answer:
- Down’s syndrome is a genetic disorder which is caused by the trisomy of chromosome 21.
- Trisomy of chromosome 21 caused due to the abnormal cell division.
- Trisomy of chromosome 21 means that the 21th chromosome has an extra copy of chromosome 21. There is no cure for Down’s syndrome, the disabilities are life long.
- However people with Down’s syndrome can live healthy lives but their mental and physical development delays.

Symptoms of Down’s syndrome:
- Flat facial features
- Small head and ears
- Short neck
- Bulging tongue
- Poor muscle tone
- Impulsive behavior
- Poor judgement
- Mild to moderate intellectual disability
- Stunted growth

Additional information:
1. Klinefelter’s syndrome – It is a genetic disorder that occurs only in the body. In this syndrome a boy born with an extra X chromosome i.e. affected person has three sets of chromosomes, XXY. Klinefelter's syndrome causes breast development, reduced muscle mass, reduced body and facial hair, etc.
2. XYY – It is a genetic disorder in which a male have an extra set of chromosome i.e. XYY chromosome instead of XY chromosome. The person affected with this order will be normal in all senses except fertility.
3. Triple X – This syndrome is characterised by the presence of an extra X chromosome in each cell of a female. The females affected with this syndrome are fully normal except they have tall stature.

Hence, option A is the correct answer for this question.

Note: All the disorders that we discussed in above discussion are the mendelian disorders. These disorders are caused from the mutation at a single genetic locus. These disorders are also inherited from the parents to offspring.