Question

What are the structural components of a eukaryotic gene?

Answer 1

Although humans contain a thousand times more DNA than do bacteria, the best estimates are that humans have only about 20 times more genes than do the bacteria. This means that the vast majority of eukaryotic DNA is apparently nonfunctional. This seems like a contradiction. Why wouldn't more complicated organisms have more DNA? However, the DNA content of an organism doesn't correlate well with the complexity of an organism—the most DNA per cell occurs in a fly species. Other arguments suggest that a maximal number of genes in an organism may exist because too many genes means too many opportunities for mutations. Current estimates say that humans have about 100,000 separate mRNAs, which means about 100,000 expressed genes. This number is still lower than the capacity of the unique DNA fraction in an organism. These arguments lead to the conclusion that the vast majority of cellular DNA isn't functional.