Chapter 10 &11

Chapter 10 &11 - Selected topics from chapter 10...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Selected topics from chapter 10 and 12 Chapter 10- Molecular Regulation Regulating Gene Expression Microbes respond to changing environment Alter growth rate Alter proteins produced Must sense their environment ( in able to respond to the changes that are occurring) Receptors on cell surface Must transmit information to chromosome Alter gene expression Change transcription rate Change translation rate Sensing the Environment Two component signal transduction 1. Sensor kinase protein in plasma membrane Binds to a signal (kinase) Food Chemical cue Activates itself via phosphorylation 2.Cytoplasmic response regulator Takes phosphate from sensor Binds chromosome
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Alters transcription rate of multiple genes Altering Transcription Rates sigma factor guides RNA polymerase to initiate transcription at promoter Proteins can help guide sigma factor to promoter Activator binds to DNA sites next to promoter Increases frequency of that gene’s transcription Proteins can block sigma factor from binding Repressor Binds to DNA sites next to promoter o Operator Lowers frequency of that gene’s transcription The amount of an enzyme in the cell can be controlled by decreasing ( repression ) or increasing ( induction ) the amount of mRNA that encodes the enzyme For negative control of transcription , the regulatory molecule is called a repressor protein and it functions by inhibiting mRNA synthesis . (repressors are roadblocks) The E. coli lac Operon Lactose ( milk sugar ) is uses as nutrient source E. coli has to produce this to be able to use lactose as food. Cannot pass through cell membrane (without help) Lactose permease allows entry
Background image of page 2
Disaccharide lactose must be cleaved into monosaccharides to be digested B(beta)-galactosidase cleaves lactose People also make b-galactosidase If not, person is lactose-intolerant The lacZ gene encodes b-galactosidase The lacY gene encodes lactose permease Need both proteins to digest lactose Operon Multiple genes transcribed from one promoter Both genes are transcribed together Repressor protein LacI (i) blocks transcription Repressor binds to operator Blocks sigma factor from binding promoter Repressor responds to presence of lactose Binds inducer (allolactose) or DNA , not both (preferentially binds allolactose) Add lactose repressor falls off operator
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/07/2011 for the course BIOL 2153 taught by Professor Larkin during the Spring '03 term at LSU.

Page1 / 12

Chapter 10 &11 - Selected topics from chapter 10...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online