A polymorphic repetitive-sequence PR1 family. Evidence for meiotic instability

Area of Science:

• Genomics
• Molecular Biology
• Repetitive DNA elements

Background:

• Mouse genomic DNA contains repetitive sequences, such as PR1.
• Strain-specific DNA variations can occur in mouse populations.
• Satellite-like DNA bands can be identified using Southern blot analysis.

Purpose of the Study:

• To characterize a BALB/c-specific repetitive DNA sequence, PR1 family B.
• To investigate the inheritance and meiotic behavior of PR1 family B in hybrid mice.
• To determine if recombination affects the presence of this extra DNA during meiosis.

Main Methods:

• EcoRI digestion of mouse genomic DNA.
• Southern blot analysis using the PR1 repetitive sequence as a probe.
• Analysis of recombinant phage clones to determine repeating unit length.
• Genotyping of F1 hybrid and N2 segregating populations.

Main Results:

• A 3.5 kb satellite-like band (PR1 family B) was detected in BALB/c mice but not in DDD/1 or MOA mice.
• The repeating unit of PR1 family B is 13.5 kb, forming a tandem array occupying ~2% of a BALB/c chromosome.
• Some N2 progeny from BALB/c x DDD/1 or MOA hybrids showed reduced intensity of the PR1 band, suggesting excision.

Conclusions:

• PR1 family B represents a BALB/c-specific repetitive DNA element.
• This extra DNA can undergo recombination and apparent excision during meiosis in F1 hybrid mice.
• The observed patterns are consistent with Mendelian inheritance, with occasional recombination events.