What does Lac a code for?

Asked By: Teotimo Godas | Last Updated: 6th March, 2020
Category: science genetics
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Explanation: In switch on condition of lac operon gene A codes for transacetylase (an enzyme), which convert lactose into its active form i.e. allolactose.

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Also asked, what do the lac genes code for?

The lac operon contains three genes: lacZ, lacY, and lacA. These genes are transcribed as a single mRNA, under control of one promoter. Genes in the lac operon specify proteins that help the cell utilize lactose. Similarly, lacY encodes a membrane-embedded transporter that helps bring lactose into the cell.

Likewise, what is lac operon and how does it work? An operon is a functioning unit of genomic DNA that contains a group of genes controlled by a single promoter. The lac, or lactose, operon is found in E. coli and some other enteric bacteria. This operon contains genes coding for proteins in charge of transporting lactose into the cytosol and digesting it into glucose.

Also, what is the role of LAC I?

The lac operon (lactose operon) is an operon required for the transport and metabolism of lactose in Escherichia coli and many other enteric bacteria. The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose.

How is lac operon induced?

When the inducer, lactose, is added, it binds to the repressor and changes the repressor's shape so as to eliminate binding to the operator. As long as the operator remains free of the repressor, RNA polymerase that recognizes the promoter can transcribe the operon's structural genes into mRNA. The operon is ON.

36 Related Question Answers Found

Is the lac operon negative or positive control?

Explanation: The lac operon exhibits both systems. It is a negative control system because expression is typically blocked by an active repressor (the lac repressor) that turns off transcription. We see this positive control of transcription happen when glucose levels decline.

What is the Z gene?

The lac Z gene is the structural gene encoding the enzyme for metabolizing galactose sugars (β-galactosidase).

Do humans have operons?

Operons are common in bacteria, but they are rare in eukaryotes such as humans. In general, an operon will contain genes that function in the same process. For instance, a well-studied operon called the lac operon contains genes that encode proteins involved in uptake and metabolism of a particular sugar, lactose.

What are the two types of operons?

Operons are of two types, inducible and repressible. ADVERTISEMENTS: Inducible Operon System – Lac Operon (Fig 6.34): An inducible operon system is a regulated unit of genetic material which is switched on in response to the presence of a chemical.

Why is lac operon leaky?


The lactose is able to be imported into the cell because the permease protein encoded by the lac operon is present at a low level when no lactose is available. In other words, the lac promoter is leaky; the proteins of the lac operon are produced at a low background level.

How do operons function?

Operon, genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell.

Is the trp operon usually on or off?

The trp operon, found in E. coli bacteria, is a group of genes that encode biosynthetic enzymes for the amino acid tryptophan. The trp operon is expressed (turned "on") when tryptophan levels are low and repressed (turned "off") when they are high. The trp operon is regulated by the trp repressor.

Do prokaryotes have introns?

Prokaryotes can't have introns, because they have transcription coupled to translation. They don't have time/space for that, since intron splicing will stop the coupling. Eukaryotes evolved the nucleus, where splicing can be done.

Is Allolactose a protein?

Allolactose is a sugar molecule that can permit protein synthesis to proceed. More specifically, it can turn on specific genes. It does this by telling the body that these genes need to be read in order to produce specific protein molecules.

How is the lac operon affected by positive control?


Positive Control of the lac Operon
Although lactose can induce the expression of lac operon, the level of expression is very low. The reason for this is that the lac operon is subject to catabolite repression or the reduced expression of genes brought on by growth in the presence of glucose.

Is trp operon inducible or repressible?

The trp operon is a repressible system. The primary difference between repressible and inducible systems is the result that occurs when the effector molecule binds to the repressor.

Where does the lac repressor bind to DNA?

The lac repressor (LacI) operates by a helix-turn-helix motif in its DNA-binding domain, binding base-specifically to the major groove of the operator region of the lac operon, with base contacts also made by residues of symmetry-related alpha helices, the "hinge" helices, which bind deeply in the minor groove.

Why is lac operon important?

The lac operon contains genes that E. coli uses for metabolizing the sugar lactose. Control of operons is important. Synthesis of RNA and protein requires considerable energy.

Is Iptg a sugar?


Dear Zhang, Lactose is a naturally occurring sugar (diasaccharide of glucose and galactose) which is metabolized by a number of prokaryotes and Eukaryotes. However IPTG is a synthetic and structural analogue of allolactose which can be used as a substrate but cannot be metabolized.

What is a super repressor?

2) lac IS : "super" repressor, repressor is always bound to the operator, always preventing transcription. repressor can't bind to the inducer. repressor can bind the inducer but can't undergo the conformation change required to get the repressor to fall off of the operator.

What is the code for a repressor protein?

An example of a regulator gene is a gene that codes for a repressor protein that inhibits the activity of an operator (a gene which binds repressor proteins thus inhibiting the translation of RNA to protein via RNA polymerase). In prokaryotes, regulator genes often code for repressor proteins.