Concept 3: Genes are a part of the chromosome and are found in pairs in somatic cells.
The idea that the genes which control a specific trait are found in pairs in somatic cells was proposed by a geneticist who never saw a gene. Gregor Mendel didn’t even know about chromosomes when he proposed this idea. He observed a pattern of inheritance in pea plants that could be explained by this idea. Now we know that genes are in pairs in somatic cells because the chromosomes are in pairs. A cell will have two of each kind of chromosomes (with the exception of sex chromosomes in one of the sexes) and therefore two of each of the genes found on those chromosomes.