One in 40 Ashkenazi Jews has a gene mutation that drastically increases the chance of certain cancers — and Gail Fisher thinks people need to know about it.

“I think it’s hugely important, hugely important,” said Fisher, deputy director of the BRCA Foundation, who will be speaking at Congregation Sherith Israel in San Francisco on Thursday, Sept. 27. “And certainly within the Jewish community.”

Sherith Israel will be hosting a panel of experts in medical research and genetic counseling to talk about the BRCA gene mutation: what it is, what it means and what current research shows about risk. Gene-testing kits will be available for eligible attendees, potentially part of a major UCSF study of the Bay Area’s Jewish population. The hope is to make sure people who might be at risk understand more about a situation that is as confusing as it is frightening.

“These events, when you are blanketing the Jewish community, are the events that really change people’s awareness of this mutation,” Fisher said.

The genes in question are BRCA1 and BRCA2. Everyone has them, but some carry mutations that are estimated to increase the risk of breast cancer by 60 to 80 percent and ovarian cancer by 20 to 40 percent. The risk of prostate and pancreatic cancer is also higher for men, as is the risk of breast cancer. But some groups are more likely to be affected.

“Unfortunately the Jewish community is at a higher risk for the mutation,” said Rabbi Jessica Graf of Sherith Israel.

While as many as one in 800 of the population as a whole has the gene mutation, one study found that for U.S. Ashkenazi Jews it’s roughly 1 in 40, or 2.3 percent — that represents a significant number of the 350,000 Jews living in the Bay Area. Graf thinks outreach is key.

“The reason we’re having the panel is because it’s education that will empower us to respond and to make informed choices,” she said.

One of the panelists is Raleigh Zwerin of Mill Valley who found out in 2015 that she and her sister had the BRCA mutation. She was 45 at the time. (Zwerin’s mother-in-law, Lonnie Zwerin, is a board member at Sherith Israel who was instrumental in setting up the event, Graf said.)

“It was not on our radar at all,” Raleigh Zwerin said.

Further testing showed that even though the sisters’ maternal grandmother had died young of breast cancer, they’d inherited the gene mutation from their father — and nothing in his family history had indicated a risk. That’s because both men and women carry the mutation, and anyone who has it has a 50 percent chance of passing it on to their kids.

Fisher said she urges men to get tested as well, not only for their own health but for the health of their existing or future children. Without testing, no one knows if they carry the mutation: Recent research shows that around half of women who have the mutation have no family history of breast cancer, according to the BRCA Foundation.

Once Zwerin found about the mutation, she had to figure out how to handle it.

“It became really clear that we had one of two options,” Zwerin said.

Unfortunately the Jewish community is at a higher risk for the mutation.

For her, the choice was clear. So 2½ years ago she had a bilateral mastectomy — the removal of both breasts — and her ovaries and fallopian tubes removed. Those surgeries reduced her risk of having the BRCA-related cancers by 95 percent. For Zwerin, it was a relief.

“Just knowing that this cancer could be growing in me, I just wanted to get those parts out,” she said.

Zwerin considers herself lucky, as having the surgeries before any cancer emerged meant she could go through the experience as a healthy person with a quicker recovery time, as well as reduce her risk.

“I’ve talked to so many people since I’ve had my surgery who haven’t been as fortunate as I was,” she added.

But just having the mutation doesn’t mean cancer is inevitable. Nor is the kind of surgery Zwerin had the only option. Another is monitoring, and Fisher calls making a choice “extremely personal.” She wants people to get tested, but to do so thoughtfully.

“I think it’s really important to consider it very carefully,” Fisher said. “It is not something to do on a whim. It is something you have to be prepared for.”

The Sept. 27 event, which will be moderated by Fisher, also will feature Lauren Ryan, a genetic counselor from gene testing company Color Genomics, which is based in Burlingame and was co-founded by entrepreneur Elad Gil.

Pamela Munster, co-leader of UCSF’s Center for BRCA Research, part of the Helen Diller Family Comprehensive Cancer Center, will be there to talk about the science. She is the principal investigator of an ongoing population study on the BRCA mutation that is about to expand to focus on the Jewish community. She herself has the gene mutation, as does Fisher. UCSF receives funding for research from the S.F.-based BRCA Foundation, which has awarded $3 million each to Stanford University and UCSF.

After the panel discussion, gene-testing kits that use saliva will be available free of charge for people who have at least one Jewish grandparent (an RSVP is requested in order to make sure enough kits are available), with results returned in around three weeks.

Genetic counselors will be on hand to explain implications of the testing. People who find out they carry the mutation can also get counseling for prevention strategies at UCSF’s Center for BRCA Research.

Fisher hopes the Sherith Israel event will illuminate the risks of BRCA mutation, let people know their options and help researchers get valuable information for their study.

“I think it’s really important as a community we bring this conversation out in the open so we can support and educate each other,” Fisher said.

“The BRCA Gene: An Evening of Education on the Latest Research,” 6:30 to 8:45 p.m. Thursday, Sept. 27 at Congregation Sherith Israel, 2266 California St., S.F. Free. Pre-registration requested. sherithisrael.org/event/brca.html