Theme 3: Modula.ng Transcrip.on
3.3.3 Transcrip,on starts at a promoter and ends at a
terminator
• Refer to "Theme 2: Transcrip5on"
19.3.2 Lactose u,liza,on in E. coli is the pioneering example
of transcrip,onal regula,on
• Jacob and Monod- In 1960s, discovered principle that product of one
gene can regulate transcrip5on of other genes through the study of how
E. coli regulates produc5on of the proteins needed for u5liza5on of
lactose
◦ Lactose: Consists of one molecule of glucose and one molecule of
galactose bonded by a β-(beta-) galactoside bond
• β-galactosidase cleaves lactose so that an organism may
obtain glucose
◦ Were the first to demonstrate an example of transcrip5onal gene
regula5on
• Jacob and Monod Experiment: How does lactose lead to the produc5on
of ac5ve β-galactosidase enzyme?
◦ Background: Ac5ve β-galactosidase enzyme is observed only in E.
coli cells that are growing in the presence of lactose.
◦ Hypotheses:
• The enzyme is always being produced, but is produced in an
unstable form that breaks down rapidly in the absence of
lactose.
• The enzyme is stable, but is produced only in the presence
of lactose.
◦ Experiment: Exposed a culture of growing cells to lactose and later
removed it. They measured amount of β-galactosidase present in
the culture during the experiment.
◦ Results:
3.3.3 Transcrip,on starts at a promoter and ends at a
terminator
• Refer to "Theme 2: Transcrip5on"
19.3.2 Lactose u,liza,on in E. coli is the pioneering example
of transcrip,onal regula,on
• Jacob and Monod- In 1960s, discovered principle that product of one
gene can regulate transcrip5on of other genes through the study of how
E. coli regulates produc5on of the proteins needed for u5liza5on of
lactose
◦ Lactose: Consists of one molecule of glucose and one molecule of
galactose bonded by a β-(beta-) galactoside bond
• β-galactosidase cleaves lactose so that an organism may
obtain glucose
◦ Were the first to demonstrate an example of transcrip5onal gene
regula5on
• Jacob and Monod Experiment: How does lactose lead to the produc5on
of ac5ve β-galactosidase enzyme?
◦ Background: Ac5ve β-galactosidase enzyme is observed only in E.
coli cells that are growing in the presence of lactose.
◦ Hypotheses:
• The enzyme is always being produced, but is produced in an
unstable form that breaks down rapidly in the absence of
lactose.
• The enzyme is stable, but is produced only in the presence
of lactose.
◦ Experiment: Exposed a culture of growing cells to lactose and later
removed it. They measured amount of β-galactosidase present in
the culture during the experiment.
◦ Results:
