Gastric cancer is the 8th most common cancer in Slovenia, and its incidence has been stabilizing in recent years. It is the disease of the elderly, as the average age of patients is over 60 years. Cancer is a heterogeneous population of cells that have lost control of controlled division. Tumour is caused by a combination of environmental and genetic factors, including genetic variations in the DNA sequence and alterations of mRNAs expression. Specific single nucleotide polymorphisms can cause chromosomal instability. This leads to impairment of various mechanisms, causing the cells to start dividing uncontrollably. Using bioinformatics tools, we selected the candidate gene NEK6, which encodes a segregation kinase. This enzyme regulates and ensures proper establishment of the mitotic spindle during cell division. Using informatics tools, we selected the polymorphism rs2416, which lies on the 3'-UTR region, and rs2065221, which is located in the intron region. The purpose of this master's thesis was to select candidate genetic variations and determine their impact on the development of gastric cancer. The analysis was performed on DNA samples from tissues of patients with gastric cancer and on DNA samples from the blood of healthy individuals. Selected statistical methods were used to define and determine the association of candidate polymorphisms with the development of gastric cancer.