The trial of Tony McCluskie, who stands accused of murdering his 29-year-old sibling, began at the Old Bailey this morning.
Prosecutor Crispin Aylett QC told the court that the pair had been at odds "for some time" due to "the defendant's habitual use of cannabis - and its most toxic form, skunk", BBC News reports.
However, he added that "the last straw" came in March last year when Mr McCluskie had left taps on at the flat they shared.
Aylett said: "Unsurprisingly, Miss McCluskie was exasperated by this. She had had enough. Later, while she was out, her friends heard her arguing on the telephone with her brother about what had happened."
The prosecutor said that after Miss McCluskie headed home to ask her brother to move out, he killed her, cut up her body and dumped it in Regent's Canal in East London.
Investigators discovered that a man matching McCluskie's description had taken a minicab to the canal on the day after his sister's disappearance.
Blood was found in the boot of the vehicle, while McCluskie's father and brother confirmed that they recognised him from CCTV images.
McCluskie has pleaded guilty to manslaughter but denies murder. The trial continues.
Gemma, who played Kerry Skinner in EastEnders, was reported missing on March 1 and was confirmed dead a week later.