. An interesting mutation in lacI results in repressorswith 110-fold increased binding to both operator andnonoperator DNA. These repressors display a “reverse”induction curve, allowing β-galactosidase synthesis inthe absence of an inducer (IPTG) but partly repressingβ-galactosidase expression in the presence of IPTG. Howcan you explain this? (Note that, when IPTG binds a repressor, it does not completely destroy operator affinity,but rather it reduces affinity 110-fold. Additionally, ascells divide and new operators are generated by thesynthesis of daughter strands, the repressor must findthe new operators by searching along the DNA, rapidlybinding to nonoperator sequences and dissociating fromthem.)
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.
. An interesting mutation in lacI results in repressors
with 110-fold increased binding to both operator and
nonoperator DNA. These repressors display a “reverse”
induction curve, allowing β-galactosidase synthesis in
the absence of an inducer (IPTG) but partly repressing
β-galactosidase expression in the presence of IPTG. How
can you explain this? (Note that, when IPTG binds a repressor, it does not completely destroy operator affinity,
but rather it reduces affinity 110-fold. Additionally, as
cells divide and new operators are generated by the
synthesis of daughter strands, the repressor must find
the new operators by searching along the DNA, rapidly
binding to nonoperator sequences and dissociating from
them.)
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