Exchange and Evolution

This chapter introduces the process of horizontal gene transfer that is originally found among bacteria, but now known to occur in other types of organisms. It describes horizontal gene transfer, which is a process wherein organisms acquire DNA from other individuals over the course of their lifetime. It also highlights the importance of horizontal gene acquisition in shaping the content and structure of genomes that occurs within and across all kingdoms of life. The chapter looks at instances of extensive horizontal gene transfer that challenge the traditional view of evolutionary lineages as ‘branching trees’, although limited horizontal gene transfer has profound evolutionary consequences. It talks about cells that reproduce asexually, which can have new combinations of alleles and polymorphisms or even entirely new genes, as DNA has been acquired from another cell in the population or from the environment.