Final answer:
A gene is a segment of DNA that encodes instructions for making specific proteins, transcribed into messenger RNA (mRNA) during gene expression. mRNA carries the genetic instructions to the cytoplasm for protein synthesis. Transcription involves initiation, elongation, and termination, producing pre-mRNA, which is modified into functional mRNA.
Step-by-step explanation:
Definition of Gene and Characteristics of Messenger RNA (mRNA)
A gene is a segment of DNA that contains the instructions for producing a specific protein or polypeptide chain. During the process of gene expression, genes are transcribed into messenger RNA (mRNA), which carries the genetic information out of the nucleus and into the cytoplasm, where it serves as a template for protein synthesis. mRNA thus plays a crucial role in translating the genetic code into a functional protein.
Transcription from DNA to Pre-mRNA
Transcription is the initial step of the central dogma of molecular biology, where DNA is used as a template to create a complementary strand of mRNA. This process includes three main stages: initiation, when the transcription machinery assembles at the promoter region; elongation, where the enzyme RNA polymerase synthesizes a single-stranded mRNA molecule by adding RNA nucleotides complementary to the template DNA strand; and termination, when transcription ends upon reaching a terminator sequence. The product of this process, pre-mRNA, undergoes further modifications before functioning as mRNA.