Which of the following events occurs directly after rna polymerase recognizes the transcription start site of a gene?
a. the polymerase strings amino acids into a polypeptide.
b. a complementary rna strand detaches itself from the dna.
c. the dna strand begins to unwind, separating the two strands.
d. free-floating nucleotides pair up with exposed dna bases

The correct answer is: c. The DNA strand begins to unwind, separating the two strands.

Transcription is the first step of gene expression in which DNA molecule is copied (transcribed) into RNA (mRNA) by RNA polymerase. The process of transcription is divided into three phases:

1.Initiation

•RNA polymerase with transcriptional factors bind to gene promoter

•RNA polymerase unwinds DNA double helix (transcription bubble is formed)

2.Elongation

•RNA polymerases adds nucleotides complementary to DNA  

3.Termination

•RNA polymerase gets to stop codon (transcribes a sequence of DNA known as a terminator)

•Formed complementary RNA strand is released from DNA-RNA complex