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Lesson starter

Lesson starter. Name the four different types of gene mutation. Identify the ones that can potentially be more harmful and give a reason for why. Point mutations : these are only minor mutations that will affect the organism only slightly or not at all Substitution Inversion

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Lesson starter

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  1. Lesson starter Name the four different types of gene mutation. Identify the ones that can potentially be more harmful and give a reason for why. Point mutations: these are only minor mutations that will affect the organism only slightly or not at all Substitution Inversion Frameshift mutations: these lead to major changes as large portions of DNA are misread Insertion Deletion

  2. Homework • LP 18 due in today • No homework = detention  • New homework – Due Thursday 28th November

  3. Today’s Title: The lac operon 25 November 2015 Aims: • (h) explain genetic control of protein production in a prokaryote using the lac operon; • Key phrases/words • Regulator gene • Lactose permease • Structural gene • Promoter region • Operator gene • Repressor protein • Operon • Control sites • ß-galactosidase RWCM: write notes to describe how protein synthesis can be controlled

  4. How is protein synthesis controlled?

  5. What you need to know • Explain the genetic control of protein production – using the lac operon as an example • Key terms you need to know....... • Operon – length of DNA made from structural genes and control sites • Structural genes – code for protein • Control sites – operator and promoter region of the DNA

  6. The lac operon • We know that....... • mRNA – codes for a particular protein • The code on the mRNA is complementary to the base sequence on the DNA template strand • Therefore that code on the mRNA is a copy of the base sequence on the DNA coding strand • Proteins are specified by mRNA

  7. Background information • Bacteria can synthesise different enzymes (proteins) depending on what food substrate they are growing on • E.Coli can synthesise over 3000 different enzymes • Enzymes involved in basic cell functions are synthesised at a constant rate • Inducible enzymes are synthesised as and when they are needed

  8. What is enzyme induction? • Discuss what you think this means and why it is important – you have 2 minutes • Share your thoughts with the class.

  9. Background information • E.Coli can adapt to its environment by producing enzymes to metabolise certain nutrients.......... • but only when those particular nutrients are present • E.Coli normally respires using glucose but can also respire using lactose (sugar found in milk/disaccharide) • Needs to synthesise ß-galactosidase & lactose permease

  10. Background information • ß-galactosidase – hydrolyses lactose into glucose & galactose • lactose permease – transport protein that becomes embedded in the e.coli membrane – helps transport more lactose into the cell • When placed in a lactose substrate, e.coli increases the synthesis of these two proteins by 1000x • Lactose triggers the enzymes production – inducer molecule

  11. Task 1 • Make flash cards of the following words with definitions on the back. • Regulator gene • Lactose permease • Structural gene • Promoter region • Operator gene • Repressor protein • Operon • Control sites • ß-galactosidase • Learning objectives • explain genetic control of protein production in a prokaryote using the lac operon;

  12. Mini Plenary • Match the components with the functions

  13. The lac operon • Lac system genes (in the bacterial DNA) form the operon – consists of structural genes and control genes. • Z - ß-galactosidase • Y - lactose permease • O – operator region – switches Z & Y on and off • P – Binding site for RNA polymerase for transcription of Z & Y

  14. If lactose is absent • Regulator gene is expressed and produces repressor protein • Repressor protein binds to the operator region (P & O) • Partially covers the promoter region (P) • RNA polymerase can’t bind – Z & Y genes can’t be translated • Z & Y are switched off

  15. If lactose is present • Inducer molecule (lactose) binds to the repressor protein • Repressor protein dissociates from the operator region • Promoter is now unblocked • RNA polymerase can now bind promoter region • Z &Y can now be transcribed – mRNA produced • ß-galactosidase /lactose permease can now be synthesised

  16. The lac operon • As a result of the 2 enzymes being made, e.coli can now..... • Take up lactose from its environment because lactosepermease acts a transport protein. • Using ß-galactosidase, lactose (disaccharide) can hydrolysed into glucose & galactose • E.coli can use these sugars for respiration • E.coli is gaining energy from the lactose

  17. Mini Plenary • What are the functions of: • Repressor protein • RNA polymerase • Regulatory gene • http://www.youtube.com/watch?gl=GB&v=oBwtxdI1zvk

  18. Task 2 • Get into groups of 3 or more • Use the large A2 paper as a story board • Each person is to cut out the parts of the lac operating system on the handout provided • Arrange the cut out parts to show the story of how the lac operon works in both the absence and presence of lactose

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