Chromosome is a packaged structure of DNA observed in the cell nucleus during metaphase stage of cell division when aligned in the equatorial plate of the cell.
Chromosomes number varies in different species which facilitates replication and distribution of the DNA to new daughter cells during cell division.
Chromosome is formed after coiling of DNA many times around proteins called histones which provides the structural support to DNA and form a special structure nucleosomes, further coil up and create chromatin loops which further coil around each other and make a full chromosome.
An isotonic solution is a solution in which the amount of dissolved material is equal both inside and outside of the cell. Water still flows in both directions, but an equal amount enters and leaves the cell. Hope this helps. :)
