House DistrictsState Rep. Marty Walsh’s district would reach into Quincy and state Sen. Sonia Chang-Diaz would pick up Dorchester precincts while losing whole neighborhoods elsewhere in Boston, according to a draft of redrawn political boundaries released Tuesday.

Walsh, a Dorchester Democrat who represents the 13th Suffolk District, would pick up a precinct in Quincy (Ward 3’s Precinct 3) under the plans, while in the Senate Chang-Diaz (D-Jamaica Plain) would lose neighborhoods like Chinatown, Fenway, Back Bay and Beacon Hill as she forays deeper into Dorchester.

If approved by the Legislature and the governor, the plans, keyed to population shifts documented by the 2010 U.S. Census, would set the political boundaries for the next decade. Because of those population shifts, each Senate district had to be redrawn to hold in the area of 163,691 residents. For the House, the number was 40,923 residents for each district.

Released by the special legislative committee tasked with the redrawing, the proposal would double to 20 the number of House districts that have a majority-minority population and add a Senate district with a majority-minority population in Hampden County The committee’s job was complicated because four Dorchester state representatives lost population under the last census.

According to Stanley Rosenberg, an Amherst Democrat and the Senate chair of the committee, most Bay State residents will still live in the district they are now situated in. “We split as few communities as possible,” he said.

Under the plan, Walsh would lose Ward 17’s Precincts 1 and 5 to state Reps. Carlos Henriquez’s 5th Suffolk District and Russell Holmes’s 6th Suffolk District, respectively. Henriquez, who also picks up Ward 17’s Precinct 9 from Walsh, and Holmes are two fellow Dorchester delegation members.

“I’m certainly disappointed to lose 17-1 and 17-5, but we were able to create majority black seats in Boston, which was a goal of this plan,” Walsh said.

Walsh also picks up Ward 7 Precinct 9 from South Boston’s state Rep. Nick Collins.

Walsh had two precincts shifted away from him during the last redistricting process a decade ago, nd they have been returned to him: Ward 16’s Precinct 1 and Precinct 12, which are currently in the districts of Henriquez and state Rep. Linda Dorcena Forry, respectively.

“I’m happy to get them back,” Walsh said. “I think overall it’s a fair map. The Dorchester delegation, we were kind of limited because we were all under-populated.”

Rep. Forry, a Dorchester Democrat, will continue to represent two precincts in Milton and will gain two precincts in Ward 17 (Precincts 10 and 11) in her 12th Suffolk District. Holmes currently represents those two precincts.

Holmes would receive five new precincts in Dorchester: Ward 14’s Precincts 2, 4, 6 and 7 and Ward 17’s Precinct 5. He would lose a few precincts in Jamaica Plain and Roslindale to state Rep. Elizabeth Malia (D-Jamaica Plain).

Holmes said he was pleased with his potential new district, noting that he picks up the areas around the new commuter rail stations at Talbot Avenue and Geneva Avenue, which dovetails with his interest in transportation issues. “From my perspective, we all had input all the way through,” Holmes said of the lawmakers.

In the state Senate, Chang-Diaz would pick up four precincts in Dorchester, including Ward 13’s Precincts 1, 2, and 4, and Precinct 1 in Ward 14. She would also grab precincts in the northern part of Hyde Park.

The proposed moves would increase the number of minority residents in her district, and Chang-Diaz, who is the Senate vice chair of the redistricting committee, pointed to increases in House and Senate seats centered on minority-majority voters. “I personally feel that’s progress we can sink our teeth into,” she said. But, she added, she wants to hear from her constituents about the proposal.

Hassan Williams, who unsuccessfully challenged Chang-Diaz in 2010 and worked with the Black Empowerment Coalition to monitor the map-making, attended the Tuesday press conference where the maps were unveiled. Asked if the proposed map made him more inclined to launch another run, Williams said, “We’ll see.”

Sen. Jack Hart’s First Suffolk District, which includes South Boston and parts of Dorchester and Mattapan, remains largely unchanged, although he picks up additional precincts in Ward 18 in Mattapan.

A public comment period will last until this coming Tuesday, when the committee will finalize its proposal and send it to the House and Senate for debates over amendments and for prepping the proposal for the governor’s desk. “It’s not a done deal yet,” Chang-Diaz said.

Advocacy groups focused on increasing minority representation in the Legislature said they were satisfied with the maps, but added they wanted to see more details. “We were looking for an increase of 10 [majority-minority House] seats throughout the state and that is the precise number the joint committee delivered,” said Kevin Peterson, co-chair of the Black Empowerment Coalition.

Peterson said his group wanted an incumbent-free state Senate seat in Dorchester and Roxbury in order to elect a black senator, and “that is one thing we’re going to push for over the comment period.”

Cheryl Crawford, co-director of the voting rights group MassVOTE and a member of the Drawing Democracy coalition, said the Senate maps mirror what her group had proposed to the committee. “Right now, we’re pretty happy,” she said.

The advocacy groups closely watched the redistricting process this year, which included 13 public hearings and testimony from 400 groups and individuals, a far cry from a decade ago. The last round of redistricting led to federal judges ordering a redrawing of maps and former House Speaker Thomas Finneran (D-Mattapan) pleading guilty to obstruction of justice during testimony in a redistricting lawsuit.

The Legislature’s redistricting committee is also in charge of redrawing Congressional maps, which are expected to be released soon.

Speculation has largely centered on a scenario that has Congressmen Stephen Lynch and Bill Keating facing off in a new district that includes the South Shore and Cape Cod. Lynch, a South Boston Democrat, also represents part of Dorchester.

Massachusetts is losing one of its 10 Congressional seats because the Bay State did not grow as fast as other parts of the country. Each of the nine Congressional seats has to hold around 727,514 residents.

Material from State House News Service was used in this report.