The study identifies and characterizes proteins involved in the early steps of double-strand break (DSB) repair in eukaryotes. The Mre11-Rad50-Xrs2 complex (MRX) initiates 5′ degradation, while Sgs1 and Dna2 degrade 5′- strands, exposing long 3′- strands at a rate of 4.4 kb/h. Deletion of *SGS1* or *DNA2* reduces resection and DSB repair by single-strand annealing between distant repeats. Resection in the absence of *SGS1* or *DNA2* depends on Exo1. In *exo1 Δ sgs1 Δ* mutants, the MRX complex and Sae2 generate only a few hundred nucleotides of ssDNA, leading to inefficient gene conversion and G2/M damage checkpoint arrest. The study provides a comprehensive model of the early steps of DSB repair in eukaryotes, highlighting the roles of Sgs1, Dna2, and Exo1 in 5′ strand resection.The study identifies and characterizes proteins involved in the early steps of double-strand break (DSB) repair in eukaryotes. The Mre11-Rad50-Xrs2 complex (MRX) initiates 5′ degradation, while Sgs1 and Dna2 degrade 5′- strands, exposing long 3′- strands at a rate of 4.4 kb/h. Deletion of *SGS1* or *DNA2* reduces resection and DSB repair by single-strand annealing between distant repeats. Resection in the absence of *SGS1* or *DNA2* depends on Exo1. In *exo1 Δ sgs1 Δ* mutants, the MRX complex and Sae2 generate only a few hundred nucleotides of ssDNA, leading to inefficient gene conversion and G2/M damage checkpoint arrest. The study provides a comprehensive model of the early steps of DSB repair in eukaryotes, highlighting the roles of Sgs1, Dna2, and Exo1 in 5′ strand resection.