In each humans colon mutations significance most

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In each human’s colon Mutations- significance Most result in non-functional or damaged genes But some will change a gene so that the protein it codes for gives the bacterium a survival AND REPRODUCTIVE advantage Survival of the fittest, these bacteria do better and outcompete ones without beneficial mutation soon, all bacteria in the population will have the beneficial new gne Mutations- Summary of Importance Mutations are the greatest source of genetic diversity in bacteria Occasionally errors in DNA replication (mutations)- occur And because bacteria reproduce very quickly copying their entire genome each time These mutations mount up and drive the Evolution of bacterial populations this is why bacteria adapt rapidly to changes in their environment HOWEVER, there are three other ways to account for bacterial diversity
These all involve HORIZONTAL GENE TRANSFER and GENETIC RECOMBINATION BETWEEN BACTERIA (no binary fission/ reproduction involved) The THREE WAYS ARE CALLED TRANSFORMATION TRANSDUCTION CONJUGATION METHOD 1: TRANSFORMATION Griffith’s “Transforming Principle” turned out to be DNA released from dead bacteria Transformation caused the harmless bacteria to become pathogenic by giving them the ability to produce a cap- sule THE ACTUAL PROCESS 1. Free DNA from a dead member of the same or similar strain of facteria is recognized and picked up by special receptors on the surface of the living bacterium Transformation Enzymes secreted by the bacterium cut DNA to a certain size DNA is taken into cell New DNA is incorporated into the bacterial genome by homologous DNA exchange A certain level of homology is required for the transfer to be made They don’t just pick up any old DNA New DNA may carry genes conferring new abilities Capsule forming ability etc This is TRANSFORMATION METHOD 2 : TRANSDUCTION of bacterial DNA by a Phage (bacteriophage) 1. Phage attacks a bacterium Phage injects its DNA (double stranded DNA- dsDNA) into its victim 2. DNA of the victim bacterium is broken up (hydrolysed) 3. New viral parts are made and assembled BUT…… In transduction, instead of incorporating its own DNA, One of the phages picks up bacterial DNA instead (it made a mistake) The viruses then lyse the bacterium Viruses are released Virus carrying bacterial DNA attacks another bacterium Phase injects DNA into the new bacterium but this DNA is bacterial DNA- not a problem for the bacterium! This bacterium incorporates the new DNA into its own chromosome Swapping out the homologous section of its DNA for the new section Result- the bacterium has new genes carried from the previous bacterial victim of the virus This= TRANSDUCTION
METHOD 3: CONJUGATION (bacterial “sex) not really sex! a one-way transfer of a single strand of DNA from a DONOR bacterium with a fertility factor (F+ in diagrams) To a RECIPIENT that does not have the fertility factor Fertility factor=~ 25 genes, most required for production of sex pili F factor may be part of the BACTERIAL CHROMOSOME, or

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