external lactose 0000 cell membrane RNA polymerase promoter The role of lac permease is to: lactose permease B-galactosidase allolactose lac repressor mRNA operator lacZ lacY lacA lac Operon Inhibit beta-galactosidase Facilitate entrance of lactose in to the bacterial cell Turn off the lac operon Manufacture mRNA
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
In bacteria, the genes that encode the enzymes of a metabolic pathway are usually clustered together with common regulatory regions. This cluster of genes along with their regulatory regions is called an operon.
The cluster of genes that regulate production of the enzymes needed for the transport and degradation of lactose occurs in an operon is called lac operon.
There are 3 structural genes in the lac operon:
- lacZ - gene encodes
-galactosidase enzyme - lacY - gene encodes -galactosidase permease
- lacA - gene encodes thiogalactoside transacetylase
When lactose is present, it enters the bacterial cell and binds with the repressor protein. Binding of lactose causes a conformational change in the repressor structure resulting in the inability of repressor to bind to the operator. This allows RNA polymerase to initiate transcription of three genes.
When lactose is absent, repressor binds to the operator prevents the RNA polymerase from transcribing the structural genes. i.e., transcription is inhibited.
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