Characterization of foldback sequences in Physarum polycephalum nuclear DNA using the electron microscope

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Foldback DNA, characterized by inverted repeat sequences, plays a role in genome structure and regulation.
• Understanding the structural organization of foldback DNA is crucial for comprehending genome dynamics.

Purpose of the Study:

• To investigate the structural characteristics of foldback DNA in the nuclear genome of Physarum polycephalum.
• To determine the size distribution of inverted repeat sequences and their associated loop structures.

Main Methods:

• Electron microscopy was employed to visualize and analyze the foldback fraction of nuclear DNA.
• Measurements of inverted repeat sequence length, loop size, and inter-sequence distance were performed.

Main Results:

• Inverted repeat sequences responsible for foldback DNA formation ranged from 150 to 3000 bases, with a number-average size of 340 bases.
• Approximately 50% of inverted sequences formed looped structures, averaging 1200 bases in loop length.
• The estimated distance between adjacent foldback sequences was between 100 and 1500 bases.

Conclusions:

• The study provides detailed structural insights into foldback DNA in Physarum polycephalum.
• The findings contribute to the understanding of genome organization and the role of repetitive DNA elements in eukaryotes.