Which describes a promoter? the first part of an operon that regulates where, when, and to what level a gene is expressed
the part of an operon that, if attached by a repressor protein, suppresses the expression of a gene
a cluster of genes that are expressed or repressed as a group
an enzyme that helps DNA unzip prior to transcription

When does a spring tide occur? question 9 options: they occur when the sun, moon, and earth are aligned. in spite of their name, these tides occur twice a year in the spring and fall. they occur on the date of the vernal equinox each year, no matter what stage the moon is in. this is why they are called spring tides. they occur when the sun, moon, and earth are at 45-degree angles from each other. this happens once every spring. they occur when the sun, moon, and earth are aligned. in spite of their name, these tides occur all year long.