The work is reported in three different studies, published by the journals Nature Genetics and Nature Medicine.
A team led by Richard Houlston of Britain's Institute of Cancer Research found six genetic variants that increase vulnerability to chronic lymphocytic leukaemia (CLL), which accounts for roughly a quarter of all leukaemia cases.
The variants occur in genes that play a role in the proliferation of so-called B cells, a type of white blood produced in the bone marrow.
Individually, these variants each contribute to a modest increase in the risk of CLL, but a person with all six faces an eight-fold increase.
Meanwhile, investigators in the United States found that a gene switched on by leptin -- a hormone that tells the brain when the body has sufficient nutrition -- is involved in appetite disorder and infertility.
The discovery was found in the brain of mice, but there are likely to be strong similarities in humans, the authors said.
"This gene is crucial to the daisy chain of signals that run between body fat and brain," lead researcher Marc Montminy of the Clayton Foundation Laboratories for Peptide Biology, said in a press release.
"It likely plays a pivotal role in how much we, as humans, eat and whether we have offspring."
Variations of the gene, called TORC1, could play a part in obesity and infertility, as they could send the wrong signals to the brain as to whether food is needed and whether the body has sufficient energy stores for reproduction.
A third study, entailing a trawl through the genetic code of thousands of people, netted two new genes involved in childhood inflammatory bowel disease (IBD), a painful condition that includes Crohn's disease and ulcerative colitis.
Genomics -- as genetic analysis is called -- is one of the most eagerly explored frontiers of medicine today.
Finding genes that cause or amplify a disease opens up pathways for diagnostic tools to help identify people at risk from the ailment.
It also, more distantly, opens up avenues for potential drugs to block or reverse the gene's malfunction.