What do viral genomes look like compared to those of living organisms? Why is their genome so small? What do prokaryotic genomes look like compared to those of eukaryotes? (review the five points in the powerpoint discussion) Why is there such a strong correlation between genome size and gene number among prokaryotes? What is a plasmid and what role do they play in bacterial genome evolution? Horizontal Gene Transfer What does gene order tell us about the frequency of genome rearrangement in prokaryotes? Solution Viral Genome Vs. Living Organism\'s Genome Characteristics VIRUS LIVING ORGANISM NUCLEIC ACID DNA/RNA DNA REPLICATION ENZYMES USE HOST\'S ENZYME PRESENT GENOME SIZE SMALL LARGE GENOME MODIFICATIONS ABSENT PRESENT SEGMENTS MONO/MULTI-PARTITE -NA- viruses have small genome size because of high mutation rate in larger genomes, to avoid erors during multiplication the size of genome is reduced. Prokaryotic genome Vs Eukaryotic genomes characteristics prokaryote eukaryote ploidy haploid diploid origin of replication single multiple chromosome shape,number circular, single linear, multiple nuclear membrane, nucleus nucleoid, no membrane present introns absent present size small with no different regions large with distinct regions in prokaryotes, there is strong correlation between genome size and gene number because prokaryotes contain total coding genes no extra non coding region as seen in eukaryotes thus there is a positive correlation. Plasmid is a extrachromosomal DNA found in bacteria which can replicate it self independently from cellular DNA. it is involved in transfer of bacterial genes to other bacteria (horizontal gene transfer) thus facilitate recombination between genes and new genetic combination. gene order are conserved in prokaryotes, but introduction of new genes by horizontal gene transfer changes gene order. thus, changes mong conserved sequence can tell about the rearrangement between genes on chromosome..