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16.1 Genetic variation in bacteria Learning objectives: • Describe the genetic material in bacteria • List the ways variation may occur in bacteria • Define the term mutation • Describe how conjugation occurs AQA AS 2010 ad Bacteria- prokaryote Sketch the structure of a simple rod shaped bacteria Label the following parts: cell wall, plasma membrane, plasmid, DNA, cytoplasm, 70s ribosomes, capsule, mesosome, flagellum Why is the genetic material not identified as a chromosome? What is a plasmid? Change over time Write a sentence or two describing the link between adaptation mutation variation Which comes first? Definitions recombining mutation survive DNA increases adaptation sexual changing Natural selection a process where a species (group of organisms) adjusts to suit a ………….. environment over time. This is called ……………. . It …………. the long term reproductive success of a species as it enables its members to ………... long enough to breed. Variation or diversity occurs by a) changing the quantity or structure of the ….., known as ………… or b) ……………… existing DNA of two individuals during …………reproduction. Variation in bacteria A. Mutations: Changes in bases sequences: CATGATTAGTAC Addition e.g. …………………………………. Deletion e.g. ………………………………… Substitution e.g. ……………………………. Explain how each of these types of mutations affect the primary structure of a polypeptide and the tertiary structure of a protein. Which could have the greatest effect on the functioning of a globular protein such as an enzyme? Give your reasoning. B. Conjugation is the transfer of DNA from one bacterial cell to another. Draw sequence of events 1. Conjugation tube produced by one cell 2. Donor cell plasmid replicates 3. Circular plasmid breaks and linear DNA passes down tube 4. Linear DNA enters recipient cell 5. Linear strand forms new plasmid A. Circular plasmid breaks C.Linear DNA enters recipient cell B. Donor cell plasmid replicates E. Linear DNA passes down tube D. Conjugation tube produced by one cell F. Linear strand forms new plasmid Conjugation is a ………..event with only some of the donor cell DNA being transferred. The recipient cell will acquire new ………………… from donor cell DNA This method of DNA transfer is known as ……………. gene transmission, i.e. between two individuals of different species. Where genes are passed from one generation to the next is known as ………………….. gene transmission. Test yourself: summary Q p219 In which two ways goes genetic diversity occur in living organisms? 2. What is a mutation? 3. Albinism can be caused by a mutation that results in organisms being unable to produce an enzyme involved in the manufacture of a chemical called melanin. Suggest a possible sequence of events, starting with a mutation and ending with cells being unable to produce melanin. 4. Distinguish between horizontal and vertical gene transmission. 1. Discovering conjugation in bacteria Strain 1 in medium + methionine and biotin required growth supplements Minimal medium Strain 2 in medium + threonine and leucine required growth supplements Minimal medium Medium plus all four supplements Strain 1 and 2 in medium + threonine, leucine methionine and biotin Minimal medium Which strains of Escherichia coli should grow on the medium that contained all the missing nutrients? 2. Which strains of E. coli would you expect to grow on the minimal medium? 3. What information had the DNA from the donor strain transferred to the recipient strain? 4. These further experiments were carried out to disprove explanations other than conjugation. Suggest one alternative explanation that might account for the growth of a few colonies on the minimal medium. 1.