module 7 lec 9 Flashcards
What is the operon theory in gene regulation?
The operon theory suggests that a single signal can regulate the expression of several genes that are clustered together and involved in the same process.
What is an operon?
An operon is a cluster of genes that are transcribed together as a single mRNA in bacteria, typically under the control of a single promoter.
What does polycistronic mean?
Polycistronic refers to an mRNA transcript that contains the coding sequences for multiple genes, which are usually part of an operon.
How are bacterial genes typically arranged for coordinated regulation?
Bacterial genes involved in the same process are often clustered together in an operon and transcribed as a single mRNA.
Why is the operon model important in understanding gene regulation?
The operon model explains how bacteria can regulate multiple genes simultaneously with a single regulatory mechanism, allowing efficient responses to environmental changes.
What happens if the inducer binding domain of the repressor is mutated?
If the inducer binding domain is mutated, it leads to constant repression of the gene, as the repressor cannot be deactivated by the inducer.
What is the effect of a mutation in the DNA binding domain of the repressor?
A mutation in the DNA binding domain causes the repressor to fail to bind to the operator, resulting in constant expression of the gene.
How does a mutation in the operator DNA sequence affect gene expression?
A mutation in the operator sequence prevents the repressor from binding, leading to constant expression of the gene.
How can mutations in the lac operon lead to constant repression?
Mutations in the inducer binding domain of the repressor prevent the repressor from being inactivated, causing constant repression of the operon.
How can mutations in the lac operon lead to constant expression?
Mutations in the DNA binding domain of the repressor or the operator sequence cause the gene to be constantly expressed, as the repressor can no longer bind properly.
What is the difference between cis and trans acting elements?
Cis acting elements affect only genes on the same DNA molecule, while trans acting elements can diffuse and affect genes on any DNA molecule in the cell.
How can we distinguish between a mutant repressor and a mutant operator?
Both can cause constitutive expression of the lac operon, but mutant repressors are trans acting (can affect any operon), while mutant operators are cis acting (only affect the lac operon on the same DNA molecule).
What are trans acting elements?
rans acting elements are factors (like mutant repressors) that can diffuse through the cytoplasm and regulate genes on any DNA molecule in the cell.
What are cis acting elements?
Cis acting elements are DNA sequences (like the operator) that influence gene expression only on the same DNA molecule they are located on.
Can cis acting mutations affect distant genes?
No, cis acting mutations only affect genes on the same DNA molecule. They cannot influence distant gene
