DNA double-stranded breaks (DSBs) induce phosphorylation of histone H2AX at serine 139, forming γ-H2AX. This phosphorylation occurs rapidly after ionizing radiation exposure, reaching half-maximal levels within 1 minute and maximal levels within 10 minutes. Approximately 1% of H2AX becomes γ-phosphorylated per gray of radiation, indicating that each DSB leads to the phosphorylation of about 2 × 10⁶ base pairs of DNA. γ-H2AX is a sensitive and rapid response to DSBs, providing insights into chromatin structure. H2AX is one of three H2A subfamilies, with H2AX comprising 2–25% of the H2A complement in mammalian tissues. It is phosphorylated at serine 139 in response to DSBs, a modification that distinguishes it from other H2A species. γ-H2AX is detected in various mammalian cells and mice after ionizing radiation, and its formation is not directly due to radiation or hydroxyl radicals but rather to DNA breaks. γ-H2AX is formed by DNA double-stranded breaks and is detected in cells exposed to ionizing radiation, UV light, or chemicals like bleomycin and hydrogen peroxide. It is phosphorylated on serine 139 and is a major component of histone gels. γ-H2AX is also detected in mice after radiation, indicating its presence in living organisms. γ-H2AX is a phosphorylated form of H2A, and its formation is confirmed by in vitro experiments using recombinant H2AX. γ-H2AX is phosphorylated on serine 139, and this site is critical for its function. Mutations in this region affect the phosphorylation efficiency, indicating that serine 139 is the primary site of γ-phosphorylation. The formation of γ-H2AX is proportional to the amount of radiation, with higher doses leading to greater phosphorylation. γ-H2AX forms rapidly after radiation exposure, reaching maximum levels within 10 minutes and decreasing over time. The amount of γ-H2AX is quantified and found to increase with radiation dose, with 1% of H2AX becoming γ-phosphorylated per gray of radiation. These findings highlight the role of γ-H2AX in cellular responses to DNA damage and its importance in understanding chromatin structure and DNA repair mechanisms.DNA double-stranded breaks (DSBs) induce phosphorylation of histone H2AX at serine 139, forming γ-H2AX. This phosphorylation occurs rapidly after ionizing radiation exposure, reaching half-maximal levels within 1 minute and maximal levels within 10 minutes. Approximately 1% of H2AX becomes γ-phosphorylated per gray of radiation, indicating that each DSB leads to the phosphorylation of about 2 × 10⁶ base pairs of DNA. γ-H2AX is a sensitive and rapid response to DSBs, providing insights into chromatin structure. H2AX is one of three H2A subfamilies, with H2AX comprising 2–25% of the H2A complement in mammalian tissues. It is phosphorylated at serine 139 in response to DSBs, a modification that distinguishes it from other H2A species. γ-H2AX is detected in various mammalian cells and mice after ionizing radiation, and its formation is not directly due to radiation or hydroxyl radicals but rather to DNA breaks. γ-H2AX is formed by DNA double-stranded breaks and is detected in cells exposed to ionizing radiation, UV light, or chemicals like bleomycin and hydrogen peroxide. It is phosphorylated on serine 139 and is a major component of histone gels. γ-H2AX is also detected in mice after radiation, indicating its presence in living organisms. γ-H2AX is a phosphorylated form of H2A, and its formation is confirmed by in vitro experiments using recombinant H2AX. γ-H2AX is phosphorylated on serine 139, and this site is critical for its function. Mutations in this region affect the phosphorylation efficiency, indicating that serine 139 is the primary site of γ-phosphorylation. The formation of γ-H2AX is proportional to the amount of radiation, with higher doses leading to greater phosphorylation. γ-H2AX forms rapidly after radiation exposure, reaching maximum levels within 10 minutes and decreasing over time. The amount of γ-H2AX is quantified and found to increase with radiation dose, with 1% of H2AX becoming γ-phosphorylated per gray of radiation. These findings highlight the role of γ-H2AX in cellular responses to DNA damage and its importance in understanding chromatin structure and DNA repair mechanisms.