Inhaltsverzeichnis
Was versteht man unter dem Operon-Modell?
Bei der Genregulation von Prokaryoten (Mikroorganismen ohne Zellkern) spricht man vom sogenannten Operon-Modell. Als Operon bezeichnet man einen DNA-Abschnitt, der aus dem Promotor (Startstelle für die Transkription), dem Operator, und mehreren Strukturgenen besteht.
Was macht die Substratinduktion?
Als Substratinduktion wird eine Enzyminduktion bezeichnet, bei der das Substrat eines Stoffwechselweges als Induktor wirkt. Bis dahin hat ebendieser das Ablesen (Transkription) eines Genbereichs unterdrückt und dadurch die Neubildung von Enzymen behindert, die für den Abbau (Katabolismus) des Substrats notwendig sind.
What is the function of inducer in lac operon?
An inducer can take away the repressor and switch on the gene. The gene then directs the structural genes to transcribe. Operator gene of lac operon is made of only 27 base pairs. It acts as an initiation signal which functions as recognition centre for RNA-polymerase provided the operator gene is switched on.
Why is the operator gene called an I-gene?
In lac-operon, it is called i -gene because it produces an inhibitor or repressor. The repressor binds to operator gene and stops the working of the latter. It exerts a negative control over the working of structural genes. It is regulator protein synthesised all the time (constitutively) by the regulator i -gene.
What is the difference between inducible and repressible operons?
A repressible operon uses a protein bound to the promoter region of a gene to keep the gene repressed or silent. This repressor must be actively removed in order to transcribe the gene. An inducible operon is either activated or repressed depending on the needs of the cell and what is available in the local environment.
How does the attenuator travel from promoter to structural genes?
The latter travels from promoter gene to structural genes provided operator gene is switched on. Two components of regulatory region occur between operator gene and structural gene E. They are leader sequence (L) and attenuator (A). The leader sequence is involved in controlling attenuator.