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Molecular Basis of Heredity: Part 2. Genomes

Author(s): Raye L. Alford, PhD

Eukaryotic Genomes

Like the extensive diversity in life forms within the eukaryote domain, the genomes of eukaryotes also vary greatly in size and composition. For example, the yeast Saccharomyces cerevisiae genome is ~12.5 million base pairs in size, while the fern Psilotum nudum genome is ~250 billion base pairs in size. Further, most eukaryotic genomes encode complex genetic elements that preserve and maintain the structure of the genome, and regulate the transcription (expression) of eukaryotic genes.

Genomes of eukaryotes contain regions known as introns. Introns are non-coding segments of DNA, of variable size, that separate the coding segments, or exons, of the genes of eukaryotic organisms. During RNA processing, the introns are removed from RNA molecules in a complex process called splicing. In addition, the genetic material of eukaryotes is organized into one or more linear structures called chromosomes.