What are the two types of binding sites on the repressor protein?
Repressors can also have two binding sites: one for the silencer region and one for the promoter.
What is an active repressor protein?
Active repressor protein. Specific chemical that binds to the region of a gene called an operator.
What is the binding site of a repressor protein?
Is the repressor protein produced in active or inactive form?
This allows transcription from the structural gene and the production of a protein. Other genes are normally active and able to be constantly transcribed, because the repressor protein is produced in an inactive form.
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.
What is the purpose of the lac repressor?
The lac repressor is a protein that represses (inhibits) transcription of the lac operon. It does this by binding to the operator, which partially overlaps with the promoter. When bound, the lac repressor gets in RNA polymerase’s way and keeps it from transcribing the operon.
What does trp operon do?
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.
What are Lac and Trp operons?
The lac operon responds to an inducer that causes the repressor to dissociate from the operator, derepressing the operon. The trp operon responds to a repressor protein that binds to two molecules of tryptophan. This binding prevents the binding of RNA polymerase, so the operon is not transcribed (Fig.
What is the process of attenuation?
Attenuation is a regulatory mechanism used in bacterial operons to ensure proper transcription and translation. In bacteria, transcription and translation are capable of proceeding simultaneously. The process of attenuation involves the presence of a stop signal that indicates premature termination.
Can attenuation occur in eukaryotes?
Prokaryotes commonly use attenuation as a mechanism to control gene expression, but eukaryotes do not. This makes attenuation possible. In eukaryotes, transcription takes place in the nucleus and most translation takes place in the cytoplasm.
Why is attenuation possible for prokaryotes and not eukaryotes?
Attenuation is made possible by the fact that in prokaryotes (which have no nucleus), the ribosomes begin translating the mRNA while RNA polymerase is still transcribing the DNA sequence. This allows the process of translation to directly affect transcription of the operon.
Why can translation begin before transcription is complete?
translation of mRNA into protein can begin even before transcription is complete (Figure 8.10). Because mRNA is produced in the cytoplasm in prokaryotes, the start codons of an mRNA being transcribed are available to ribosomes before the entire mRNA molecule is even made.