The genes that are expressed and the quantities at which those genes are expressed define an organism's phenotype.
Gene expression may be affected by mutations in the DNA.
Structural genes are coding sequences that include the genetic code for the proteins needed to carry out the operon's function.
Inducible operons often have a catabolic function (digesting molecules) and are switched off in the absence of the proper inducer molecule.
The lac operon's role is to create the proteins needed to digest the sugar lactose.
Lactose acts as the lac operon's inducer molecule.
When glucose levels fall, cAMP levels rise in the cell.
The trp operon's job is to create the enzymes required to manufacture the amino acid tryptophan.
Epigenetic alterations are reversible modifications to the nucleotides of the DNA sequence, such as nucleotide methylation (adding a methyl group).
Euchromatin is DNA that is more loosely coiled around histone proteins, making it more accessible to RNA polymerase and resulting in higher gene expression in the euchromatin.
The timing of transcription factor expression throughout development is crucial for the generation of specialized tissues and organs from a single-celled zygote.
Mutations in this gene, or expression of this gene at an inopportune moment, can result in legs not developing or legs growing in the incorrect body segment.
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