The answer is nitrogen. It comprises
approximately 78% of the atmospheric air.
Nitrogen can be found in most life
processes including as a component of amino acids –amino group (NH3-). It is also involved
in the structure of nucleosides that are critical
in the formation of nucleotides and ATP.
The phrase "main component of atmospheric air" already points to nitrogen as it makes up 78% (mole basis) of atmospheric air. Nitrogen is the main element found in amino acids (amino group refers to NH3) and amino acids make up almost all important life molecules such as proteins, DNA, and ATP.
Sexual reproduction happens when there is the involvement of two parents to give rise to the offsprings.
For the production of offsprings, each of the parents produces a haploid gamete and it is by the fusion of these two haploid gametes that a diploid organism is produced.
In the given situation, there are 19 chromosomes present in the haploid gametes this means that a diploid individual will have 2X19 = 38 chromosomes.
Now the underground stem cells are not gametes but somatic cells and the somatic cells are diploid and hence, they will have 38 chromosomes.
