For each of the E. coli strains that follow, indicate theeffect of the genotype on the expression of the trpEand trpC genes in the presence or absence of tryptophan. [In the wild type (R+ P+ o+ att+ trpE+ trpC+),trpC and trpE are fully repressed in the presence oftryptophan and are fully expressed in the absence oftryptophan.]R = repressor gene; Rnproduct cannot bind tryptophan; R− product cannot bind operatoro = operator for the trp operon; o− cannot bind repressoratt = attenuator; att− is a deletion of the attenuatorP = promoter; P− is a deletion of the trp operonpromotertrpE− and trpC− are null (loss-of-function) mutationsa. R+ P− o+ att+ trpE+ trpC+b. R− P+ o+ att+ trpE+ trpC+c. RnP+ o+ att+ trpE+ trpC+d. R− P+ o+ att− trpE+ trpC+e. R+ P+ o− att+ trpE+ trpC−/R− P+ o+ att+trpE− trpC+f. R+ P− o+ att+ trpE+ trpC−/R− P+ o+ att+trpE− trpC+g. R+ P+ o− att− trpE+ trpC−/R− P+ o− att+trpE− trpC+
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.
For each of the E. coli strains that follow, indicate the
effect of the genotype on the expression of the trpE
and trpC genes in the presence or absence of tryptophan. [In the wild type (R+ P+ o+ att+ trpE+ trpC+),
trpC and trpE are fully repressed in the presence of
tryptophan and are fully expressed in the absence of
tryptophan.]
R = repressor gene; Rn
product cannot bind tryptophan; R− product cannot bind operator
o = operator for the trp operon; o− cannot bind repressor
att = attenuator; att− is a deletion of the attenuator
P = promoter; P− is a deletion of the trp operon
promoter
trpE− and trpC− are null (loss-of-function) mutations
a. R+ P− o+ att+ trpE+ trpC+
b. R− P+ o+ att+ trpE+ trpC+
c. Rn
P+ o+ att+ trpE+ trpC+
d. R− P+ o+ att− trpE+ trpC+
e. R+ P+ o− att+ trpE+ trpC−/R− P+ o+ att+
trpE− trpC+
f. R+ P− o+ att+ trpE+ trpC−/R− P+ o+ att+
trpE− trpC+
g. R+ P+ o− att− trpE+ trpC−/R− P+ o− att+
trpE− trpC+
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