![]() ![]() The cell cycle diagram shows that a cell division cycle consists of 4 stages: Įukaryotic cells reproduce genetically identical copies of themselves by cycles of cell growth and division, instead of by binary fission. Mitosis results in two new cells with identical DNA to each other, where the entire cell cycle begins again. Cells that stop dividing exit the G1 phase of the cell cycle into a so-called G0 state. Interphase consists of G1, DNA synthesis (DNA), and G2 phases. The cell cycle shows interphase (I) and mitosis (M). Plasmid transfer is a common vehicle for antibiotic resistance to spread between bacterial species. The DNA transferred can be in the form of a small circular plasmid or a hybrid of both plasmid and chromosomal DNA. In conjugation, DNA is transferred from one prokaryote to another by means of a pilus, which brings the organisms into contact with one another. Archaea are not affected by bacteriophages but instead have their own viruses that translocate genetic material from one individual to another. ![]() Transduction results in a recombinant organism. In transduction, bacteriophages, the viruses that infect bacteria, sometimes also move short pieces of chromosomal DNA from one bacterium to another. If a nonpathogenic bacterium takes up DNA for a toxin gene from a pathogen and incorporates the new DNA into its own chromosome, it too may become pathogenic. In transformation, the prokaryote takes in DNA found in the environment this DNA has been shed by other organisms. Binary fission does not provide an opportunity for genetic recombination, a benefit of sex that we will read about next time, but bacteria and archaea can share genes by three other mechanisms: transformation, transduction, and conjugation. The key ingredient in asexual reproduction is the faithful replication of the DNA into each new cell, because DNA contains the full set of instructions to make everything that new cell will need for life. The cell, now enlarged, pinches inward at its equator and separates into two cells, which are clones of each other, genetically identical to the parent. The circular chromosome (the DNA) is replicated and the cell grows, separating the two resulting chromosome copies from one another. ![]() Reproduction in bacteria and archaea is asexual and usually takes place by binary fission. Bacteria and Archaea reproduce asexually, by simply dividing a parent cell into two new cells in a process called binary fission. ![]() Sexual reproduction, like we and most animals have, is actually pretty unusual. Who reproduces asexually? Almost everyone but us It can occur with or without sex! The tricky bit in reproduction is to make sure that each offspring has a full set of DNA, which contains all the genes that encode life. Reproduction, the production of offspring, is an essential step in the life cycle.
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