What are Genetic Markers?

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  • Written By: Mary McMahon
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Genetic markers are sequences of DNA which have been traced to specific locations on the chromosomes and associated with particular traits. They demonstrate polymorphism, which means that the markers in different organisms of the same species are different. A classic example of this type of marker is the area of the DNA which codes for blood type in humans: all humans have and need blood, but the blood of individual humans can be very different as a result of polymorphism in the area of the genome which codes for blood.

There are a number of applications for genetic markers. One of the most obvious is in tracing the inheritance and history of traits, from eye color to genetic diseases. Understanding which areas of the genome are involved in inheritance of particular traits can help researchers understand these traits, and this can sometimes be applied to the diagnosis and treatment of disease. For example, several genetic markers are associated with an increased risk of breast cancer, and women with these markers can opt for more aggressive preventative care to address this risk.


Genetic markers are also used in paternity testing and the investigation of crimes. By looking for specific markers, known samples of DNA can be compared to unknown samples or samples in question to determine whether or not the samples are related or identical. DNA testing usually includes comparisons of several alleles, not just one, to confirm that the similarities between the samples are actually meaningful.

Some genetic markers are whole genes, while others are snippets of DNA which do not necessarily serve a function. They can appear at one point in the genome, or in multiple areas, sometimes on different chromosomes. They can also consist of strands of repeating DNA; polymorphism these repetitious strands are of immense interest to scientists studying inheritance of numerous traits.

The variations between genetic markers in two people can sometimes be very subtle, but these small variations can make a huge difference. Once the genome was sequenced, researchers began to focus on identifying genetic markers so that they could learn more about how the genome was arranged. Identifying new markers is a painstaking process which includes processing DNA from related individuals or people with the same genetic condition to find commonalities which could be used to pinpoint particular traits. Especially when markers appear at multiple points in the genome and interact with each other, tracking them down can be very challenging.


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Post 11

If George's great-great-great grandson has 67 markers that match 67 markers of Andrew's great-great-great grandson, what is their relationship?

Post 9

@rugbygirl - Thanks for pointing out that genetic markers can be relevant for things that we don't usually think of as "genetic disorders."

There's an argument to be made that the only solution to the problem you raise is a national single-payer health care system (i.e., socialized medicine, like they have in the UK and Canada), that any other system would make abuses possible. The bestselling author Robin Cook, who is also an MD, favors this solution even though in the past, he was actually against medical insurance except for catastrophic illnesses and injuries. Being someone who writes medical thrillers, he of course envisions a future in which health insurance companies will find ways to bump off patients

likely to be expensive!

I don't know if I think his solution is the only one, though. I'd like to hear other ideas for having genetic information be available to individuals (and their doctors) if they want it, while preventing health insurance companies from acting on it.

Post 8

@ anon158679 - It might help if you think of "genetic markers" as just being a more generic term than "genes." People might talk about having "the breast cancer gene" or "the colon cancer gene," but many traits are determined by multiple genes.

As medicine's capability of determining your chances of developing various diseases with genetic components continues to grow, we need to think about how it will affect our traditional system of medical insurance. Should people have to pay higher health insurance premiums - or worse, be denied health insurance at all - just because they have the bad luck to be born with a higher chance of developing cancer, diabetes, or some other condition? How can we prevent that?

Post 6

What else could better explain genetic markers?

Post 2

Wow, this really helped with my extended essay! Thanks!

Post 1

This is a great intro to genetic markers!

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