1. AP Biology Chapter 18

2. I can describe how genetic variation occurs in bacteria.

3.  Prokaryotic cells Lack nuclei Lack membrane- bound organelles (have ribosomes for protein synthesis) May have flagella for movement May have capsule around cell wall Various shapes, arrangements

4.  Single, circular bacterial chromosome in nucleoid region  Often contain one or multiple plasmids “Bonus” genes independent of bacterial chromosome Code for traits such as antibiotic resistance, fertility factors

5.  Even though bacteria are asexual, they are not clones!  Variation introduced by: Mutations  Chromosome and/or plasmid replication Transformation Transduction Conjugation Transposable elements/transposons

6.  Changes in DNA during replication  Grow and divide FAST, so errors happen and get passed on quickly  Ex: drug resistant bacteria

7.  Alteration of a bacterial cell’s genotype and phenotype by the uptake of naked, foreign DNA from the surrounding environment  Ex: harmless Streptococcus pneumoniae bacteria can be transformed to pneumonia-causing cells

8.  Phages carry bacterial genes from one host cell to another  Generalized transduction – random genes are transferred  Specialized transduction – genes adjacent to prophage site in temperate phages

9.  The direct transfer of genetic material between cells  Bacterial ‘sex’

10.  Transposable genetic elements “jumping genes”  Pieces of DNA that move around within the genome

11. I can describe how bacterial cells use the operon system to regulate gene expression.

12.  Prokaryotes must use substances and synthesize macromolecules fast enough to meet their needs  If enzymes aren’t needed, genes for their production must be “off”  Conservation of resources

13.  Genes grouped together operating together in prokaryotic cells  Can be inducible Normally “off” but able to turn “on” when needed  Can be repressible Normally “on” but able to turn “off” when not needed  Coordinated control of genes required for metabolism

14. I can identify and explain the functions of the following structures with regard to the operon system.

15.  Promoter Region of DNA that signals for RNA polymerase to bind  Operator Region of chromosome to which the repressor binds when the operon is turned “off”  Repressor A protein that suppresses the transcription of a gene  Regulatory gene Codes for production of the repressor protein  Structural gene Codes for enzyme product  Inducer Molecule that binds to and changes repressor’s shape

17. I can use the trp operon as an example to describe a repressible operon and explain how this system works.

18.  Repressible Genes are normally “on” and produce tryptophan for the cell If tryptophan is present, genes are turned “off” and tryptophan in the environment is utilized

19.  Cell requires tryptophan for metabolism Typically has to make it for itself  To do this: Repressor is inactive and not bound to the operator Promoter is available to RNA polymerase Structural gene is transcribed mRNA is translated into enzymes Enzymes produce tryptophan

20.  No tryptophan present in environment  Cell makes its own tryptophan-producing enzymes

21.  If the cell has adequate supply of tryptophan, it turns the operon “OFF” and uses what is available Save resources – don’t make it if it’s already there!  To do this: Tryptophan binds to the repressor, activating it Activated repressor binds to the operator This blocks RNA polymerase from transcribing mRNA No genes are transcribed  no proteins produced

22.  Tryptophan is present in environment  No need to produce tryptophan producing enzymes

23.  McGraw Hill McGraw Hill

24.  Inducible Genes are normally “off” in absence of lactose If lactose is present, genes are turned “on” and enzymes to digest it are produced

25.  If no lactose if present in the cell, no lactose-digesting enzymes are produced Save resources – don’t make it if it’s not needed!  To do this: Active repressor binds to operator This blocks RNA polymerase from transcribing mRNA No genes are transcribed  no proteins produced

26.  No lactose in environment  No need to produce lactose-digesting enzymes

27.  Lactose is not normally present If it is, bacteria will digest and use it  To do this: Allolactose inducer binds to repressor, inactivating it Inactivated repressor cannot bind to operator RNA polymerase can bind to promoter Genes coding for lactose-digesting enzymes transcribed mRNA is translated into enzymes that digest lactose  When lactose supply is depleted, inducer separates from repressor, allowing it to bind to operator again and block transcription

28.  Lactose is present in environment  Enzymes to digest it are produced

29.  McGraw Hill McGraw Hill