CJG Blog

Center for Jewish Genetics blog

Are all BRCA mutations alike?

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DNAstrand2By Haley Fuoco

You may have heard that individuals with Jewish ancestry have a greater risk of BRCA mutations, linked to breast and ovarian cancers, and other types of cancer. But did you know that not all mutations in the BRCA genes are the same? There are actually around 2,000 variations (a technical term for genetic differences) of BRCA1 and around 3,000 variations of BRCA2. These variations are formally known as Single Nucleotide Polymorphisms, or SNPs.

The term polymorphism describes two or more changes in a particular DNA sequence that arise from heritable mutations and act as genetic markers in the DNA. As the name suggests, a SNP is a type of variation at a single base pair in the DNA sequence.

An example of a SNP might look like the DNA strands below:



where the G and the C base pairs represent different versions of a particular DNA sequence. Even though SNPs are common, and they arise from mutations, they typically do not cause changes to the DNA that lead to disease.

Scientists and healthcare providers can learn more about certain genetic disorders, as well as genetic lineage, by examining SNPs. Since SNPs are heritable, they can often track the inheritance of diseases in families or populations. One specific example of this is with BRCA1 and BRCA2 mutations in individuals with Ashkenazi Jewish ancestry. About one in 40 individuals with Ashkenazi Jewish ancestry carry a BRCA mutation. And despite the many different types of BRCA mutations caused by SNPs, most individuals with Ashkenazi Jewish ancestry with a BRCA mutation have the same type. Why is this the case?

This occurrence is likely caused by the founder effect, a concept that suggests that individuals with Ashkenazi Jewish ancestry can trace their ancestry back to a small group of “founders” who lived 500 years ago in Eastern Europe. SNPs allow scientists to trace Ashkenazi Jewish ancestry back to the founder population. The founder effect explains why individuals of Jewish ancestry have the same BRCA1 or BRCA2 SNPs. Therefore, not all BRCA mutations are the same, but some BRCA mutations might be more common in individuals with similar ancestry.


Better Together: Newborn & Carrier Screening

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By Carol Guzman

You might be looking into genetic carrier screeningbut, if you’re under the age of 60, there’s a good chance you’ve already had a different kind of genetic test before.

How? Nearly every baby in the United States receives genetic screening within 48 hours of birth.

Newborn screening has several differences from carrier screening. But they both provide parents with information to help them have healthy children. In Illinois, the newborn screening panel currently includes more than 60 early-onset diseases and guides doctors toward quicker treatment of them.

The list of conditions is regularly growing. In late June, the screening test issued by the Illinois Department of Public Health added spinal muscular atrophy (SMA). The Recommended Uniform Screening Panel, a list of conditions recommended to states by the federal government, added SMA to its panel in 2018. Thirty-one states now screen for SMA, a disorder characterized by the child having weak muscles and loss of muscle control.

For many genetic disorders included in newborn screening panels, therapy and treatment can begin right away.  For SMA in particular, early therapy can effectively prevent the loss of motor neuron cells. Dr. Mary Schroth, the chief medical officer for Cure SMA, says parents “ need to think very quickly about which of these treatments is most appropriate…without a lot of time to think about what to do” after their newborn’s diagnosis.

Fortunately, carrier screening prior to or early in pregnancy can help parents-to-be anticipate what disorders their child(ren) may face earlier on in the process, giving them more time to make informed decisions. Unlike newborn screening, carrier screening panels test adults to see whether they are carriers of genetic mutations that cause certain conditions. If both parents are carriers for same recessive genetic mutation – for this example, the one that causes SMA – each of their children has a 25% likelihood of having SMA, a 50% chance of carrying the SMA-causing mutation without health effects, and a 25% chance of not carrying the mutation at all.

The American College of Obstetricians and Gynecologists recommends that  women who are considering pregnancy or are pregnant have carrier screening for SMA, cystic fibrosis, various hemoglobinopathies, fragile X syndrome, and Jewish genetic diseases including Tay-Sachs disease. Screening is especially important for those with European Jewish ancestry, as many conditions occur more frequently in those individuals. In fact, screening can test for hundreds of genetic diseases tailored to an individual’s family health history and ethnicity.

Carrier screening provides carrier couples more time to assess their family planning options. Newborn screening also helps identify babies with serious illnesses. While both tests are crucial to bringing a baby into the world, carrier screening is not always offered to individuals planning for a family. Do not rely on the newborn screening alone, consider talking to a doctor or a healthcare provider to discuss carrier and newborn screening when family planning.

To learn more about the Sarnoff Center’s affordable, accessible carrier screening program or to speak with a genetic counselor, visit  Jewishgenetics.org/cjg/get-screened  or contact us at GeneticScreening@juf.org

Does Cancer Really Skip Generations?

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By Haley Fuoco

Unfortunately, most of us know someone whose life has been touched by cancer in some way. In some families, multiple people have received cancer diagnoses, which could be a sign of hereditary cancer. Sometimes, cancer diagnoses appear every other generation, leading to a misconception that cancer can skip generations. Although it may look like certain cancers only show up in every other generation, this might not be the case. In medical genetics the term reduced penetrance describes genetic disorders that seemingly skip generations.

Penetrance is the measurement of how often a certain trait occurs given a certain genetic marker or vice versa. Some disorders show complete penetrance, which means all individuals with a certain genetic marker will express that specific disorder. An example of a genetic disorder with complete penetrance is neurofibromatosis type 1, where everyone with the genetic marker for this disorder will show symptoms of this disorder. However, some disorders show reduced penetrance.

 Reduced penetrance occurs when an individual has a genetic marker for a disorder but may never develop that disorder. Reduced penetrance is often seen in hereditary cancers, specifically those related to theBRCA1 and BRCA2 genes. There is no guarantee that individuals with BRCA1 or BRCA2 mutations will develop cancer, but they do have a higher chance to develop cancer compared to those without a cancer mutation. Some individuals with a mutation in their BRCA1 or BRCA2 genes may develop cancer during their lifetimes, but some will never develop cancer. This is exactly why it may seem like cancer skips generations in a family. While the underlying cause of reduced penetrance is still unknown, researchers believe that a combination of genetic, environmental, and lifestyle factors all play a role.

Reduced penetrance can also complicate the interpretation of family health history, but a genetic counselor can help. To start, collect your family’s health history as far back as possible. This might be a challenge for some families but collect what you can and share it with a healthcare provider. The Sarnoff Center website provides helpful tools to help individuals document family health history and provides information on how to asses your risk. The team, and specifically the genetic counselor at the Sarnoff Center, is available to answer any questions or connect you to more resources related to cancer genetics.



Affordable, Accessible Genetic Screening in Illinois

Our affordable, accessible carrier screening program uses advanced technology to provide comprehensive screening for Jewish and interfaith couples. Visit our Get Screened page to learn more and register.


Do You Know What's In Your Genes?

What is the most valuable gift you can give to your family? The gift of good health! There are many health conditions that run in families. Knowing your family health history can alert you to the potential risk for a variety of genetic disorders . Talk to your relatives for warning signs and assess your risk for hereditary cancers.

Did you know: Ashkenazi Jews are 10 TIMES more likely to have BRCA mutations, which significantly increases lifetime risks for hereditary cancers, so what does this heightened risk mean for you? Click here to learn more .