Final answer:
The sigma subunit recognizes and binds to the -35 and -10 sequences of prokaryotic promoters, which are similar across different bacterial species and are crucial for the initiation of transcription.
Step-by-step explanation:
The sigma subunit initially recognizes and binds to the -35 and -10 sequences of prokaryotic promoters during the initiation of transcription. These sequences are known as consensus sequences, which means they are similar across various bacterial species (b. they are similar in all bacterial species). However, it is important to note that while they have a similar function, they are not identical in every bacterial species. The -35 sequence is specifically recognized by the sigma factor of the RNA polymerase to facilitate the binding of the polymerase to the DNA, enabling it to begin transcription.