Question

what controls the timing of gene expression?
regulatory sequence for a gene
coding sequence for a gene
nucleotides that dictate the sequence of amino acids in the protein
alleles for a gene
transgenic portion of a gene

Explanation:

Regulatory sequences control gene - expression timing. They can include promoters, enhancers, and silencers that respond to various signals to turn gene expression on or off at the appropriate time. Coding sequences code for proteins, nucleotides in the coding region determine amino - acid sequence, alleles are different forms of a gene, and the transgenic portion is foreign DNA inserted into a gene, none of which control the timing of gene expression.

Answer:

regulatory sequence for a gene