What are genetics and genomics?

What are genetics and genomics?

Cancer care has come a long way over the past decade, driven in large part by discoveries related to DNA. But there is still confusion among the general public about what all this means. This misinformation can blur patients’ understanding of how to benefit from available treatments and may discourage them from pursuing certain options. The words “hereditary” and “genomic,” for example, are often used interchangeably, although their meanings are quite different, especially when it comes to cancer treatment.


Genetics refers to the inherited traits that are passed from one generation to the next generation through the set of genes. Through genetic testing, scientists study the molecular makeup of a particular patient, identifying abnormalities or predispositions they may have been born with and how they might affect disease risk and other health effects.

For example, the BRCA1 gene has been linked to an increased risk of breast cancer. Genetic testing came to the fore in 2013, when actress Angelina Jolie announced she had undergone a preventive double mastectomy after discovering she carried a BRCA1 gene mutation. A person who inherits an altered copy of the BRCA1 and/or BRCA2 genes has an increased risk of developing breast and ovarian cancer.

Genetic testing is not for everyone. It is generally recommended for people with a family history of cancer or other diseases, including a history of:

  • Diagnosed with breast, colon or uterine cancer before age 50
  • Inherited genetic mutation
  • Ovarian cancer is diagnosed at any age
  • The same type of cancer is diagnosed in two or more close relatives
  • The same type of cancer in several generations of the family.


Whereas genetics involves the study of a patient’s molecular makeup, cancer-related genomics involves decoding the DNA structure of cancer cells. Genomic tests, for example, can reveal characteristics that drive a tumor and tell you how quickly it is growing and where it has spread. Tests can also detect abnormalities in the cancer that may be affected by some medications.

Because both areas of study involve examining the effects of genetic abnormalities, people, and even some clinicians, often confuse the two terms. “The important thing here is to understand that we’re talking about two very different types of DNA,” says Dr. Murray Markman, chief of medicine and science at Cancer Treatment Centers of America. ® (CTCA). “Personally, I would use the term ‘hereditary’ to refer to genes present in an individual from birth, and I would use the word ‘genome’ to describe genes that might be unique in a tumor. Certainly, this is not a convention that everyone uses, and that adds to the confusion.”

As clinicians use genetics to learn more about single-gene diseases and genomics to better understand specific genetic mutations and complex diseases such as cancer, this could lead to early diagnoses, new interventions, and targeted therapies. Think of it as fighting cancer with a missile rather than a bomb.

This is especially true of advanced genomic tests, which raise the profile of tumors through genetic mapping analysis. The test may be an option for patients with hard-to-treat cancers who have tumors that haven’t responded adequately to conventional treatments. This type of personalized care, often called precision cancer care, examines the molecular makeup of a tumor to determine whether the most appropriate treatments are available. “By detecting abnormalities in the cancer, you may be able to adjust for that abnormality and make treatment more accurate,” says Dr. Markman.

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