Which step in transcription occurs first? mRNA moves the code from the nucleus to the ribosome for protein production. A gene is expressed through protein production. RNA polymerase attaches to the promoter. A repressor protein must attach to the operator.

RNA polymerase attaches to the promoter

Explanation:Took the test

(C) RNA polymerase attaches to the promoter.

Explanation:

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.