THE EFFECT OF X-RAYS ON CHROMOSOMES IN DIFFERENT STAGES OF MEIOSIS

Area of Science:

• Cytogenetics
• Radiation Biology
• Molecular Biology

Background:

• Chromosome abnormalities can arise from various environmental factors.
• Understanding radiation sensitivity at different cell cycle stages is crucial for predicting genetic damage.

Purpose of the Study:

• To investigate the relationship between x-ray dosage and chromosome abnormalities in pollen mother cells.
• To identify specific stages of meiosis and mitosis that are most sensitive to x-ray-induced damage.

Main Methods:

• Exposure of pollen mother cells to varying low dosages of x-rays at different developmental stages.
• Microscopic analysis of chromosome configurations during the first meiotic anaphase.

Main Results:

• Maximum frequencies of chromosome abnormalities were observed following irradiation of buds in the pachytene stage of meiotic prophase and preceding mitosis.
• A linear relationship was found between x-ray dosage and the frequency of abnormalities.
• Calculated diameter of the sensitive chromonema volume approximates that of protein molecules, with the linkage mechanism comprising ~90% of this volume.

Conclusions:

• The x-ray-sensitive portions of chromonemata are closely paired during pachytene and early mitotic prophase.
• Chromonemata appear to be two-parted during synapsis, with division occurring between pachytene and anaphase and during mitotic prophase.
• The findings provide insights into the structural organization of chromosomes and their sensitivity to radiation, with implications for understanding gene-level effects.