In her youth, her parents often told her the stories of Starfleet Captain Hikaru Sulu which was one of the reasons why she decided to attend Starfleet Academy. Once there, the began her career in the sciences and learnt more about the history of Captain James T. Kirk. During her time there, she beat the Kobayashi Maru scenario by reprogramming the simulator which allowed her to win against the setting. By the middle part of the century, she had attained the rank of Commander and was assigned to the Oberth-class science vessel, USS Tobias and sought to make a career in the science field similar to the one that was attained by Kathryn Janeway on the USS Voyager and a career in the command field similar to the one that was attained by James T. Kirk on the USS Enterprise. While on board the ship, she formed a close friendship with the ship's chief medical officer; Doctor Andrea M'Benga who she nicknamed Bones.
In 2374, the Virogen Crisis fell upon the United Federation of Planets leading to a massive relief mission that was untaken by Starfleet as many inhabitants were infected whilst the food stores were dying from the plague. Commander MacDonald was sent to the planet Chal along with her crew in order to tend to the natives which included the Chalchaj 'qmey. Christine along with most of her crew beamed onto the surface where they tried their best to help the natives even though their supplies were low. She later assisted her chief engineer, the Tellarite Barc in trying to fix the Replicators through the parts that they had available. Her camp was visited by a mysterious stranger who came to the world and was seeking a native who he wished to pay his respects to and asked for commander MacDonald's help. Helping the stranger with the computers, she determined that the person was still alive but had been infected with the Virogen plague. The stranger also gave Commander MacDonald a dedication plaque that he wished to give to the infected patient. It was there that Christine read the plaque and was shocked to read that it was a dedication plaque to the USS Enterprise-A.
Christine believed that the stranger was in fact the famous Starfleet Captain James T. Kirk and voiced her suspicions to her friends. Andrea M'Benga did not believe it was true and stated that Kirk died at Veridian III where he was buried by Jean-Luc Picard. However, Commander MacDonald was not convinced of this and believed that he had in fact survived. Meeting the stranger once more, she helped him meet with the patient called Teilani where he treated her with a special herb that seemingly cured her of the Virogen infection after which he took her away. MacDonald became gradually more convinced that it was Kirk but did not press the matter until their base came under attack from Orion pirates. Beaming the stranger onto the Tobias, she pressed him into service and made it clear to him that she knew who he was. Together, they were able to repell the Orion attackers and their mothership after which they examined one of the crashed fighters only to learn that their attackers were not Orions; they were in fact Vulcans. Christine took the Tobias to the planet Vulcan with Kirk by her side in order to learn the truth of the attack and the Virogen plague.
Arriving on the planet, she met with Ambassador Spock and his aide Srell in the Gonthar District where they were also attacked by a mysterious group. In order to learn more about this threat, MacDonald dispatched a forensic team to learn more but they were all arrested by the Vulcan authorities who believed they were responsible for the attack and even mutinied against Starfleet. Facing a Vulcan Magistrate, they were placed in the holocell detention facilities onboard the Vulcan space station whilst her ship was impounded until they conferred with Starfleet. Commander MacDonald was placed in a cell with Srell, Barc and Andrea whilst Kirk and Spock shared another cell. Christine managed to uncover a way to fool the holographic sensors allowing them to escape onto the USS Tobias where they attempted to power it to escape. During this escape attempt, Srell was seemingly killed by one of the Vulcan guards during a fire fight. The Tobias was nearly detained by the USS Enterprise under the command of Jean-Luc Picard but they managed to evade the ship after which they headed for Tarsus IV. Christine was at first confused about this course change but it was revealed to her that Kirk was in fact a survivor of the Tarsus IV Massacre and that the world was a test bed for the Virogen plague which they suspected were the actions of the Symmetrists movement.
The USS Tobias was nearly destroyed once they orbited the planet when Transporter mines were beamed onto their path but they were saved by the timely arrival of the Enterprise. The two crews later beamed onto the surface where they determined that it was indeed a Symmetrist base which was developing the Virogen. The two crews later faced a fire fight with the Symmetrists which pinned them down. Kirk was initially going to distract the enemy by drawing away their fire but Christine stopped him after which she passionately kissed him before making a run for it which focused the enemy weapon fire on her. She managed to evade the attack but was incapacitated by Srell who was alive and was a member of the Symmetrists. Holding her hostage, she was rescued by an attack by Spock along with Kirk. During the confrontation, Srell was killed and the Symmetrist ended along with their Virogen plague when a cure was found which was distributed around the infected colonies. (TOS novel: Avenger)
She was later promoted to the rank of Captain and continued to serve on the USS Tobias which she commanded during the Dominion War. During that time, she took the vessel which discovered a Pakled probe when they were approached by a Jem'Hadar fighter who believed that the Starfleet vessel had found a piece of Borg technology. They would have been destroyed had Captain MacDonald managed to delay the Vorta after which she destroyed the Tobias in order to save her crew. She was later awarded a new ship, the USS Pathfinder, an Intrepid-class vessel though Doctor M'Benga was temporarily reassigned to Deep Space 9 at the time. (TOS novel: Dark Victory) Christine later received orders in 2374 to protect a Ferengi asset at the planet Halkan who were conducting an experiment on the world's Dilithium crystals]]. It was there she was reunited with Kirk and Picard who warned her that the experiment had grave consequences and that they were all being manipulated by the Preservers. Captain MacDonald did not believe them at first and took offense to the fact that they suggested that the Preservers were responsible for manipulating her career in order to make her their unwitting agent. She was deeply offended when Andrea, who had accompanied Kirk on the Enterprise, suggested that Christine was being aggressive because she was hurt that Kirk left her for Teilani. However, they were ultimately successful in stopping the Preservers plans to destroy the Mirror Universe but this came at the cost of Teilani's life. (TOS novel: Preserver)