codes for the production of a repressor protein

1. A regulator gene is a prokaryotic gene that codes for the production of a repressor protein An operator is a DNA segment that controls transcription by blocking RNA polymerase with a repressor protein; it is part of the operon. An intron is a section of a gene that is transcribed but not translated. An exon is a section of a gene that is transcribed and translated. A transcription factor is a protein that facilitates gene transcription by binding to RNA polymerase and to an enhancer.

2. C D A B D

3. A series of genes whose transcription is controlled by a single promoter and operator. Lactose bonds to the repressor protein, releasing it from the operator. This allows the lactase genes to be transcribed and translated. In the absence of lactose, the repressor protein binds to the operator, preventing 
transcription of the lactase genes. Without a nuclear envelope, there is no structure to separate newly 
synthesized RNA from ribosomes. Therefore, ribosomes can begin to 
translate the RNA as soon as it is formed, before it has had a chance to 
be modified.

4. lactose repressor protein promoter operator regulator gene

5. If the regulator gene were deleted then the repressor protein could 
no longer be produced. Without a repressor protein at the operator 
site, RNA polymerase would transcribe genes continuously. Transcription is activated because the lactose molecule has bound to the repressor 
protein. This causes the repressor protein to release from the operator site, which then 
permits RNA polymerase to transcribe the structural genes.