How does antibiotic resistance arise and how can resistance spread?

i. How does antibiotic resistance arise? antibiotic resistance = bacteria that cannot be treated with antibiotics resistance arises when bacterial genes mutate (=a change in base sequence of DNA) - leads to the formation of proteins that in some way make the bacterium resistant to the killing action of the antibiotic. genes can be found in both the main bacterial chromosome or in the plasmid (small ring of additional DNA)several ways in which proteins can bring about resistance: the protein breaks down the antibiotic the protein alters membrane permeability so that the antibiotic can't enter the cell, or so that the antibiotic is rapidly pumped out of the cell the protein provides an alternative metabolic pathway (so that the pathways disrupted by the antibiotic is not required for survival)
ii. How does resistance spread? Vertical gene transmission: between the same species of bacteria passing the resistance allele from mother cells to daughter cells bacteria reproduce asexually, so each daughter cell will have an exact copy of the parent cell's genes, including the alleles that produce bacterial resistance Horizontal gene transmission: interesting because it means resistance can be passed between different species 2 bacteria join together: conjugation plasmids containing resistance alleles are then copied and transferred through a stalk (= the pilus)end up with both bacterial cells having a copy of the antibiotic resistance gene