DNA, RNA, Chromosomes, and Genes

Genetics and the Human Genome

Why is the human genome such a small size?

The process of translation uses an mRNA pattern to produce a string of amino acids technically known as a polypeptide. To turn a polypeptide into a protein with the shape that is crucial to its function requires several more steps. Sugars, lipids, phosphate groups, or other molecules may be added to the amino acids in the chain. The polypep-tide may be “trimmed” as well; the first few amino acids may be removed. Some proteins, like insulin, only become functional after cleavage by an enzyme. Because of this ability to create variations from the basic polypeptide chain, a given gene may code for several different functional structures. This helps to explain the unexpectedly small size of the human genome. Our genes actually code for several hundred thousand different proteins. While most proteins fold spontaneously into their specific conformation, some require the help of other molecules to achieve this. Chaperone proteins guide newly synthesized polypeptides into their functional three-dimensional shape.


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