Carol Marcus

Dr. Carol Marcus was a female Human who was one of the Federation's leading molecular biologists of the 23rd century.

Starfleet career
In the early 2250s, Marcus attended Starfleet Academy alongside James T. Kirk and Gary Mitchell. During their time at the Academy, Marcus became romantically involved with Kirk, but their relationship came to an end in 2254, when he cheated in the Kobayashi Maru scenario and abused her trust.

By 2260, Marcus had graduated from the Academy and achieved the rank of lieutenant. Despite commendations for her superb work as a scientist, Marcus also earned several reprimands for minor insubordination and an unwillingness to follow orders.

In 2260, Lt. Marcus was assigned to the USS Eagle (NCC-956), under the command of Captain Botwin. Also serving aboard at this time was Commander Kirk, who was serving as Botwin's first officer. For the first few months they managed to avoid contact with each other, but Botwin ordered Kirk to try and set Marcus straight and make sure she became an excellent Starfleet officer. Over the next few months, the pair got reacquainted and once again became romantically involved.

The relationship came to an end following the Eagle's mission to Caperna IV, where Marcus' ignorance of an order from Commander Kirk led to a landing party becoming endangered. Thankfully, all members of the party returned safely to the Eagle and Marcus was placed on report by Kirk. Shortly after, Marcus resigned from Starfleet after discovering that she was pregnant with Kirk's child. 

In 2261, Marcus was working for Kraden Interplanetary Research. 

That year, Marcus gave birth to a son, David. 

Scientist
Considered an expert in molecular biology, bio-protein development, cell mutation and radiation, she was offered many posts in the Federation, but kept being refusing to get involved in projects with potential military applications. 

In 2266, she was assigned by the Federation Council to the meta-genome project at Starbase 47 as a civilian overseer. It was here, realizing the potential of the meta-genome, that Marcus first envisioned developing a technology that could create entire star-systems from scratch. 

In 2267, Carol and her son David then attended Sam Kirk's funeral, though she did not want her son to meet his father. 

By 2268, she had transferred to the ARK-7 space station to continue work with Dr. Anthony Cheever, eventually developing a device called the cradle, which contained scores of microscopic life forms. Her team also accidentally created a virus during the course of their research which was deadly to Vulcanoid life forms. Thinking that the station was creating a weapon to be used by the Federation to commit genocide against the Romulan people, a Romulan force led by Centurion Preax boarded the station and took Doctor Marcus and Cheever prisoners. The crew of the USS Enterprise (NCC-1701) arrived to investigate the situation. Upon boarding the station Spock was infected with the virus, which made him seriously ill. Dr. Leonard McCoy worked rapidly to find a cure for the virus, curing Spock and the Romulans on board the station, and freeing the captives. Satisfied that the creation of the virus was an accident, the Romulans left Federation space peacefully. 

Apparently using the knowledge gained from the meta-genome project, Dr. Marcus invented the Genesis device and in 2284, received Federation support for the project. Project Genesis was classified as top-secret and housed at the Regula I space station located near the Mutara Nebula. 

The Genesis Disaster
In 2285, the Reliant discovered the planet Ceti Alpha V whereupon the ship was commandeered by the infamous Augment Khan Noonien Singh who learned of the vessels mission. He attempted to get more information on Project Genesis from his nemesis, Admiral James T. Kirk but was thwarted in his plan. He later traveled to the Regula facility where he was looking for the Genesis device and killed many of the station's personnel. Using a mind controlled Pavel Chekov, he learned of the prototype being located in a bunker on Regula and used the transporter to beam the device onto the Reliant. However, Admiral Kirk attempted to stop him and during the skirmish between the two, the Genesis device was detonated which killed Khan in the Mutara Nebula. The resulting explosion resulted in the formation of the Genesis Planet due to the energy matrix within the Genesis device. 

Later Life
Following the Project Genesis disaster in 2285, Marcus was forced to live the rest of her life under tight security, lest her top-secret knowledge of Genesis fall into unfriendly hands.

She lived a secluded life on the world of Pacifica, under the constant watch of Starfleet security officers. She was allowed to leave her exile whenever she wanted, but seldom did as she was required to bring along an entourage of bodyguards to protect her from any enemy who might desire the Genesis information. 

In 2293, early in the year, Marcus was critically wounded during a Klingon attack upon the Federation colony world of Kudao; a weapons-test for General Chang's prototype Bird-of-Prey capable of firing while cloaked. Near the end of the year, attended Kirk's memorial service that was held on the grounds of Starfleet Academy. Also in attendance were former crewmembers of the USS Enterprise (NCC-1701) and some of his other old "acquaintances". 

In 2310, Marcus, along with Dr. Gillian Taylor and Captain Uhura of the USS Hermes (NCC-10376), planned to test an experimental Genesis Device on Pacifica. However, Marcus and Taylor encountered intelligent life in Pacifica's ocean and the plan was abandoned. (SS TOS (The Hero of My Own Life))

In 2375, she was kidnapped by a race of shape-shifting Moss Creatures who tricked her into revealing the secrets of the Genesis Device. The moss-creatures used the Genesis technology to re-form entire sections of space for re-settlement. Marcus was killed in the explosion of the moss-creatures headquarters. She willingly stayed behind so that no other race could gain the knowledge of Genesis from her. 

Alternate timeline
In an alternate timeline in which John Frederick Paxton destroyed Starfleet Command and ended the talks for the Coalition of Planets in 2155, Carol Kirk married Commander James T. Kirk, the first officer of the UESS, in 2255. They had a son named David Samuel Kirk, who was born in 2261.

In 2264, she and David were killed when their transport vessel, the Galileo, was travelling to an interstellar symposium on molecular biology proposed by the Vulcan government. Upon the sight of a human vessel crossing the border of the Interstellar Coalition, the ship was destroyed by the Coalition vessel ICV when its Vulcan captain T'Prynn claimed that the human transport was not responding to hails. This led to her husband developing a deep resentment towards Vulcans.