Population refers to an array of organisms of the similar species, which thrives in a particular geographical region and interbreed. The three main characteristics of a population are density, size, and dispersion.
The density signifies towards how many organisms are thriving in a specific region. The size refers to how big a population is, and dispersion signifies towards the degree of spreading of the particular population.
DNA is a chain of nucleotides bonded together. On that chain there are particular portions of it that the sequence of the nucleotide codes for particular proteins; this is known as a gene. In eukaryotric cells, DNA is coiled around proteins such as histones to form chromatids which when two join at the centre by a centromere to form a chromosome.