Question

The process of transcription begins with which nucleic acid and ends with which one?

Short answer

Transcription begins with DNA and ends with mRNA.

Step-by-step solution

Identifying the Starting Nucleic Acid

Transcription is the process through which the DNA in a cell's nucleus is used as a template to create an mRNA molecule. It starts with DNA being unzipped by the enzyme RNA polymerase.

Identifying the Ending Nucleic Acid

The process of transcription ends when a strand of mRNA is produced. Messenger RNA (mRNA) is synthesized based on the sequence of bases on the DNA template, and it carries the genetic information to the ribosome where it is translated into protein.

Summarizing the Process of Transcription

Transcription begins with DNA and ends with the creation of mRNA. The newly formed mRNA strand carries the genetic information from the DNA out of the nucleus to ribosomes in the cytoplasm.

Key concepts

DNA as Template

The blueprint for life - DNA - holds the instructions for proteins, critical molecules that perform a vast array of functions necessary for life. During transcription, a specific segment of DNA serves as a template for the creation of messenger RNA (mRNA).

This process starts with the unwinding of the DNA helix, making one of the strands accessible. As RNA polymerase travels along this strand, it matches RNA nucleotides with their complementary DNA bases. Adenine pairs with uracil (replacing thymine in RNA), and cytosine pairs with guanine.

Importance of Accuracy

Ensuring the correct transfer of genetic codes is crucial since any mistakes could result in faulty proteins. The DNA's role is akin to a stencil that ensures every copy is consistent with the original design.

mRNA Synthesis

mRNA synthesis is a cornerstone of gene expression. After DNA serves its purpose as a template, RNA polymerase synthesizes a single-stranded mRNA molecule.

The mRNA synthesis kicks off at a specific location on the DNA called the promoter region. RNA polymerase then stitches together RNA nucleotides to form a strand of mRNA that is complementary to the DNA template sequence.

Processing of mRNA

Before the mRNA can be utilized for protein synthesis, it undergoes several modifications, such as the addition of a 5' cap, polyadenylation at the 3' end, and splicing to remove non-coding regions, known as introns. These steps modify the pre-mRNA to become mature mRNA, ready for translation.

Role of RNA Polymerase

RNA polymerase is the key enzyme that carries out transcription. It is responsible for reading the DNA template and assembling the RNA nucleotides to form mRNA. This process is complex and highly regulated.

RNA polymerase binds to the promoter, pries apart the DNA strands, and initiates mRNA synthesis without the need for a primer, which is necessary for DNA replication. The enzyme works tirelessly, moving along the DNA, adding nucleotides one by one in the 5' to 3' direction until it reaches a termination signal, signaling the end of the gene.

Ensuring Fidelity and Regulation

RNA polymerase not only synthesizes RNA but also plays a role in ensuring the correct nucleotides are incorporated, thereby minimizing errors. Additionally, various factors can enhance or inhibit the activity of RNA polymerase, thereby controlling gene expression.

Genetic Information Transfer

The transfer of genetic information from DNA to mRNA is fundamental to the central dogma of molecular biology, which describes the flow of genetic information within a biological system.

Transcription is the first step in this transfer process. The DNA unwinds, and RNA polymerase reads the sequence of the DNA template strand, creating mRNA that mirrors the genetic code. This mRNA then exits the nucleus and travels to the ribosomes in the cytoplasm.

From Code to Function

At the ribosomes, the sequence encoded by the mRNA is translated into the amino acid sequence of a protein, culminating in the manifestation of genetic information as a functional product. It’s a process that underpins development, physiology, and the very essence of life itself.