Species radiation by DNA replication that systematically exchanges nucleotides?

Area of Science:

• Molecular Biology
• Genetics
• Evolutionary Biology

Background:

• RNA and DNA synthesis share similarities, leading to the hypothesis of 'swinger' RNA transcripts.
• Functional pressures favor the existence of swinger DNA over swinger RNA due to DNA's long-lived nature.
• Specific nucleotide exchange patterns (A<->T, C<->G, A<->T+C<->G) can conserve RNA self-hybridization properties.

Purpose of the Study:

• To investigate the potential existence and implications of 'swinger' DNA replication.
• To explore the role of swinger DNA in evolutionary processes, particularly speciation.
• To identify specific instances and mechanisms of swinger DNA formation in eukaryotes.

Main Methods:

• Bioinformatic analysis of GenBank sequences, focusing on rRNA genes.
• Examination of nucleotide exchange patterns, specifically A<->T+C<->G transformations.
• Comparative analysis of swinger DNA sequences in brachyuran crabs and human rRNA.

Main Results:

• Nuclear eukaryote swinger DNA sequences in GenBank are predominantly rRNA genes exhibiting A<->T+C<->G exchanges.
• In brachyuran crabs, A<->T+C<->G swinger 18S rDNA was found in 25 species, correlating with their evolutionary radiation.
• Swinger repeats within human rRNAs provide independent evidence for swinger polymerization mechanisms.

Conclusions:

• Swinger DNA replication, particularly via A<->T+C<->G exchanges, is a plausible molecular mechanism.
• This process does not invert sequence direction, distinguishing it from inverted repeats.
• Swinger replication may represent an unexpected driver of ultrafast speciation.