How do dominant traits work

When it isn't working, you get a buildup of red pigment and end up with red hair. All it takes to keep from having red hair is a little bit of MC1R protein. So it's easy to see why red hair is recessive. As long as you have one working MC1R gene, you won't have red hair. The working protein picks up the slack. If both copies of your MC1R gene code for broken proteins, then you'll have red hair.

These kinds of dominant and recessive alleles help explain brown and probably green eyes. They may also help explain traits like whether you have hanging or attached earlobes, and whether you put your left or right thumb on top when you cross your hands.

Sometimes having only one normal copy of a gene just isn't enough. Our cells need a certain dose, or amount, of certain proteins. If we have one broken copy, the normal copy can't always pick up the slack. This is called haploinsufficiency. One example of this is a protein called CD2AP, which helps our kidneys filter out the bad stuff from our blood. People with one broken copy of CD2AP still have kidney disease, even though they have one good copy of the gene around.

One copy just doesn't make enough filters for our blood. We need two good copies to get the job done. And there are lots of other situations. Sometimes the recessive allele is the normal one and the dominant allele is a broken version.

Sounds crazy, right? Well, this can happen if the broken protein does something new, or gums up the works somehow. This is pretty complicated stuff, so we'll compare it to a basketball team to make it a little easier to understand. I hope it helps!

One way a protein can gum up the works is by getting in the way of the normal version. This can happen because each protein has many different jobs. Sometimes a broken protein can carry out one of its jobs just fine but it can't carry out its second job. When this happens, the broken protein gets in the way of normal proteins that are trying to do the second job. Imagine a basketball team. Four of the players know how to catch and shoot the ball, but the fifth player only knows how to catch the ball -- she can't shoot it.

Every time that fifth player catches the ball, the shot clock expires and the team loses possession of the ball. So even though there are four good players on the team, the fifth player like the broken protein prevents the team from winning.

This situation is called a dominant negative allele. An example of an allele like this sometimes happens in the p53 gene.

The p53 protein is very important for making sure our cells don't grow too fast. Certain alleles have mistakes in their p53 gene so that the cells grow too fast and cause cancer. Each p53 protein is like a member of the basketball team. Huntington's disease, for instance, is a dominant mutation where, if one is carrying that version of the Huntington gene, that mutation, that dominant mutation, will give the individual the disease regardless of what that person's other Huntington's disease gene allele is.

That other Huntington's disease gene allele can be perfectly normal, but the person still has the disease because of that one copy of the Huntington's disease gene that is mutated. That is dominance. Christopher P. Austin, M. Featured Content. Introduction to Genomics. Looking at this, you might conclude that the dominant phenotype is twice as common as the recessive one.

But you would probably be wrong. Recessive alleles can be present in a population at very high frequency. Consider eye color. Eye color is influenced mainly by two genes, with smaller contributions from several others. People with light eyes tend to carry recessive alleles of the major genes; people with dark eyes tend to carry dominant alleles. In Scandinavia, most people have light eyes—the recessive alleles of these genes are much more common here than the dominant ones.

Mode of inheritance has nothing to do with whether an allele benefits an individual or not. Take rock pocket mice, where fur color is controlled mainly by a single gene. The gene codes for a protein that makes dark pigment. Some rock pocket mice have dark fur, and some have light fur. The dark-fur allele is dominant, and the light-fur allele is recessive. But not all diseases alleles are recessive. Keratin proteins link together to form strong fibers that strengthen hair, fingernails, skin, and other tissues throughout the body.

There are several genetic disorders involving defects in keratin genes, and most of them have dominant inheritance patterns. To see how defective keratin genes can lead to a genetic disorder, see Pachyonychia Congenita.

What are Dominant and Recessive? The terms are confusing and often misleading Dominant and recessive inheritance are useful concepts when it comes to predicting the probability of an individual inheriting certain phenotypes, especially genetic disorders. The sickle-cell allele. Inheritance patterns Sickle-cell disease is an inherited condition that causes pain and damage to organs and muscles.

Protein function If we look at the proteins the two alleles code for, the picture becomes a little more clear. Common Myths Explained. Dominant alleles are not better than recessive alleles Mode of inheritance has nothing to do with whether an allele benefits an individual or not. APA format:.