The Concept Of Dominant And Recessive Genes

Most people have often wondered why some people have a physical trait that they don’t. Like maybe why your friend has dimples and you don’t, or why their eyes are blue and yours are a deep brown. These differences are caused by genes, which all contain specific information about why some part of you is the way it is.

Everyone inherits two copies of each gene from their parents, and the copies can either be different or the same. If the copies are different, then one is going to mask the effects of the other. The gene that trumps over the other is usually known as the dominant gene, and the weaker gene is known as recessive. In the presence of a dominant gene, a recessive gene will not manifest its traits. When two recessive genes are paired however, their traits will be manifested. Dominant genes are also the ones whose traits are manifested in the offspring. For recessive traits to be manifested, both parents have to carry that recessive gene singly or in a pair.

Genes are usually termed as dominant or recessive for a number of reasons. It’s first important to note that genes are simply an instruction manual that is used to make certain protein. The protein made is what is actually responsible for the traits that are presented physically, like red hair or blue eyes. Since we have two copies of each gene (courtesy of both of our parents), the ‘instruction manual’ in your mother’s genes may be slightly different from the one in your father’s. The combination of these two sets of instructions will cause the formation of a slightly different protein. The reason why some genes are dominant and other recessive all lies in the making of the proteins. When a gene makes a protein that is functional, then that gene is dominant. If the protein formed is broken, then the gene that has formed it is recessive.

A good example of this is the occurrence of red hair, which happens when a crucial protein in hair pigmentation fails to convert the red pigment to black, thus causing a build up of the former. If this protein is even slightly functional, then the person will not have red hair. Therefore, the presence of a working protein is all that is needed to override the broken protein’s function. This is where the concept of dominant and recessive genes is derived.

However, one working protein isn’t always enough, and may not be able to make up for the other protein’s brokenness. Sometimes the broken protein is the one that wins out, like in the formation of cancerous cells. A broken version of the protein that prevents our cells from growing too fast may attach itself to the working protein, and override its function. This is what causes the formation of cancerous cells.

In conclusion, a dominant gene doesn’t necessarily mean that the trait presented is normal or standard. In fact, some dominant genes are responsible for genetic diseases like Huntington’s Disease, which is a type of dementia.

  • Updated September 9, 2017
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