How does glucose affect the lac operon?
The lac operon has an added level of control so that the operon remains inactive in the presence of glucose even if lactose also is present. High concentrations of glucose catabolites produce low concentrations of cAMP, which must form a complex with CAP to permit the induction of the lac operon.
Why is the the ability of glucose to affect transcription of the lac operon an advantage for the bacterial cell?
why is the ability of glucose to affect transcription of the lac operon and advantage for bacterial cell? glucose is preferred sugar for the bacteria. now the RNA polymerase will bind to the lac promoter and cause transcription of the genes needed to make enzymes (lacZYA)needed for lactose metabolism.
What is the role of glucose in regulating lac operon expression?
The lac repressor senses lactose indirectly, through its isomer allolactose. Catabolite activator protein (CAP) acts as a glucose sensor. It activates transcription of the operon, but only when glucose levels are low. CAP senses glucose indirectly, through the “hunger signal” molecule cAMP.
How does glucose affect the lac operon quizlet?
How does glucose affect the lac operon? When glucose levels are low, cAMP levels are high. cAMP binds to and activates the CAP protein, allowing it to bind to the DNA.
What happens when both glucose and lactose are present?
If both glucose and lactose are both present, lactose binds to the repressor and prevents it from binding to the operator region. The block of lac gene transcription is thus lifted, and a small amount of mRNA is produced. Lactose still prevents the repressor from binding to the operator region.
Is lac operon positive or negative?
The lac operon is a negatively controlled inducible operon, where the inducer molecule is allolactose. In negative repressible operons, transcription of the operon normally takes place. Repressor proteins are produced by a regulator gene, but they are unable to bind to the operator in their normal conformation.
What turns the lac operon off?
An operon is a group of genes that are regulated together. When lactose is not present, the DNA-binding protein called ► lac repressor binds to a region called the operator, which switches the lac operon off. When lactose binds to the repressor, it causes the repressor to fall off the operator, turning ► the operon on.
What are two potential devices that eukaryotic cells use to regulate transcription?
Two potential devices that eukaryotic cells use to regulate transcription are A) DNA methylation and histone amplification.
What is a major disadvantage to a bacterial cell of having an operon?
What is a major disadvantage to a bacterial cell of having an operon? If there is a mutation in a regulatory region, none of the proteins will be synthesized. RNA polymerase. They give the cell tight control over transcription.
How does glucose repress the expression of the lac operon quizlet?
how does glucose repress the expression of the lac operon? the presence of glucose in the environment inhibits the production of cAMP, thereby preventing the binding of CAP to the DNA.
How the presence of glucose will affect expression of the Ara operon?
In the presence of glucose, the concentration of cAMP declines, preventing CAP binding and thereby decreasing the expression of the Lac operon.
What are the three important features of the lac operon?
The lac operon consists of three structural genes: lacZ, which codes for β-galactosidase, which acts to cleave lactose into galactose and glucose; lacY, which codes for lac permease, which is a transmembrane protein necessary for lactose uptake; and lacA, which codes for a transacetylase that transfers an acetyl group
How does breakdown of glucose inhibit transcription of the lac operon quizlet?
How does glucose effect the lac operon? A) When glucose levels are high, glucose binds to and deactivates the repressor, preventing it from binding to the DNA.
How is the expression of lac operon genes affected by positive control?
Regulation of the lac Operon The activity of the promoter that controls the expression of the lac operon is regulated by two different proteins. One of the proteins prevents the RNA polymerase from transcribing ( negative control ), the other enhances the binding of RNA polymerase to the promoter ( positive control ).
What happens if tryptophan levels are high?
When levels of tryptophan are high, attenuation causes RNA polymerase to stop prematurely when it’s transcribing the trp operon. Only a short, stubby mRNA is made, one that does not encode any tryptophan biosynthesis enzymes.