Question

Haploid number is 10. What shall be the tetrasomic number?
A. 22
B. 18
C. 20
D. 19

Answer 1

Hint: Haploid is also called monoploid and it means that there is only a single copy of each chromosome. Diploid organism has two sets of chromosomes or a pair.

Complete Answer:
- Ploidy is the number or set of chromosomes present in the nucleus of a cell. Based on the number of chromosomes present in the cell, the organism is classified as Haploid, Diploid, Triploid, Tetraploid and so on. Polyploidy is a condition in which an organism possesses more than 4-5 sets of chromosomes.
- When only a single copy of chromosome is present, such an organism is called haploid. During meiosis, the germ cells contain half the number of chromosomes, that is haploidy. (N)
- In normal body cells, the chromosomes exist in pairs.such organism is a diploid. It is represented as 2N. When there is an extra set of chromosomes, then the condition is called triploidy. This is a rare abnormality.
- Tetrasomic number or tetrasomy is a condition when there is a gain of extra two chromosomes of the same type in an organism. It is represented as $2N+2$.

 The question says the haploid number is 10. Which means $N=10$. In tetrasomic condition, $2N+2$ is the chromosomal composition
Hence, the tetrasomic number would be:
$\Rightarrow 2N+2=2(10)+2 $
$\Rightarrow 20+2=22$ , is the tetrasomic number

From the given options, option ‘A’ is the correct answer.

Note: Some cells have an abnormal number of chromosomes, that is not a whole multiple of the haploid number. This condition is called aneuploidy.