The present disclosure relates to genetic markers and methods of diagnosing and screening for late-onset Alzheimer's disease (LOAD). As such, the disclosure encompasses a whole-genome association analysis of single nucleotide polymorphisms (SNPs) of which a number are located within the GRB2-associated binding protein 2 (GAB2) gene as well as other markers associated with other genes. The disclosure identifies two novel haplotypes within the GAB2 gene, i.e., a LOAD risk-enhancing and a LOAD risk-decreasing haplotype. These haplotypes modify LOAD risk differentially in combination with APOE alleles. Further encompassed are therapeutic methods and agents of decreasing the deterioration of cells associated with LOAD.