Combinatorial epigenetics, "junk DNA", and the evolution of complex organisms.

Area of Science:

• Evolutionary Biology
• Genetics
• Epigenetics

Background:

• Complex functions in higher organisms often require multiple mutations to arise simultaneously.
• Small population sizes in higher organisms reduce the probability of simultaneous beneficial mutations.
• Regulatory evolution is a key process in evolutionary change.

Purpose of the Study:

• To explain how simultaneous mutations for complex functions can occur in higher organisms.
• To investigate the role of epigenetic modifications and non-coding DNA in facilitating coordinated genetic changes.

Main Methods:

• Proposed a model involving epigenetic trends and chromatin structure changes in eukaryotes.
• Examined the role of non-protein-coding sequences, including SINEs and LINEs ('junk DNA'), in regulatory evolution.
• Considered mechanisms like intrachromosomal spreading and interchromosomal 'gene kissing' for epigenetic effects.

Main Results:

• Epigenetic changes can alter transcription rates across multiple genes, mimicking simultaneous mutations.
• Low specificity requirements for mutations in non-coding DNA increase the probability of epigenetic conjunctions.
• Inheritable epigenetic changes (epimutations) can precede and be assimilated by specific genetic mutations.

Conclusions:

• A partnership between epigenetic modifications and genetic mutations facilitates the evolution of complex functions.
• Non-coding DNA ('junk DNA') plays a crucial role in chromatin structure and regulatory evolution.
• This epigenetic-genetic interplay is vital for the evolution of complexity in organisms.