Question

What are the chromosome numbers in the following?
(I) Synergid cell in the Gossypium.
(II) Leaf cell in allium.
(III) Primary endosperm nucleus in Saccharum

(a) 48,16,36 respectively.
(b) 52,26,32 respectively.
(c) 26,16,120 respectively
(d) 48,96,24 respectively.

Answer 1

Hint: Chromosome numbers are the correct number of chromosomes for a species. Chromosome number is the same for a particular species and differs for different species. An increase or decrease in the particular chromosome number generates abnormalities.

Complete answer:
Synergids are the part of the female gametophyte/embryo sac that develops from meiosis in diploid megaspore mother cell i.e., gametogenesis and hence are haploid cells. Since in the case of Gossypium, the diploid chromosome number (2n) is 52 so the synergids (n) will contain 26 chromosomes. Leaf cells are the diploid cells that carry the same chromosome number as is found in other somatic cells of that species. As it is known that the diploid chromosome number (2n) in the case of Allium is 16 so its leaf cells (2n) will also have 16 chromosomes. The primary endosperm nucleus (PEN) is defined as the product of the triple fusion which is the process of fusion of the haploid male gamete with the diploid secondary nucleus/central cell and results in the formation of triploid endosperm (3n). Since it is observed that the haploid chromosome number in the case of Saccharum is n = 40 so its primary endosperm nucleus (3n) will also have 120 chromosomes.

So the correct answer is ’26,16,120 respectively’.

Additional Information:
In any given asexually reproducing species, the chromosome number is usually an equivalent. In sexually reproducing organisms, the number of chromosomes within the body cells are diploid that is 2n condition and twice the haploid (1n) number found in the case of gametes. The haploid number is produced during meiosis. In some sexually reproducing organisms, individuals could also be produced from unfertilized eggs and thus are haploid.

Note: Having the correct Chromosome number is very critical for making a human correct. Having incorrect chromosome numbers leads to various disorders and thus the correct chromosomal number in a chromosome makes the real you. For example..the correct order for a human's chromosome number is 23 pairs, if the number varies, It can lead to various disorders and abnormalities.