Heterozygous insertions alter crossover distribution but allow crossover interference in Caenorhabditis elegans

Area of Science:

• Genetics
• Molecular Biology
• Cell Biology

Background:

• Crossover distribution on meiotic bivalents is crucial for proper chromosome segregation.
• Homolog recognition, alignment, and interference regulate crossover placement.
• Previous studies indicated bivalent structure is necessary for interference.

Purpose of the Study:

• To investigate the effect of sequence homology disruption on meiotic interference.
• To determine if a break in sequence homology impacts interference similarly to a physical break.
• To analyze crossover distribution in Caenorhabditis elegans with large insertions.

Main Methods:

• Developed a precise method for locating crossovers on Caenorhabditis elegans chromosomes.
• Analyzed crossover distribution in wild-type and heterozygous insertion mutants.
• Quantified crossover number and location relative to insertion sites.

Main Results:

• Wild-type Caenorhabditis elegans exhibit complete interference, with one crossover per bivalent.
• Animals heterozygous for large insertions maintained one crossover per bivalent, indicating interference spans homology gaps.
• Insertions locally disrupted crossing over but did not eliminate interference.
• Crossover distribution was biased, with higher frequency near homolog recognition regions.

Conclusions:

• Meiotic interference can operate across large sequence homology gaps.
• Nonhomologous sequences can cause heterosynapsis, affecting distal crossover distribution.
• Alignment can be reestablished after significant homology disruptions, allowing for continued interference.