DNA to Protein Process Name: Transcription and Translation
The process of creating proteins from the genetic information stored in DNA is a fundamental process in all living organisms. This process has two main stages: transcription and translation.
Transcription: DNA to RNA
Transcription is the first step in gene expression. It involves the synthesis of a messenger RNA (mRNA) molecule from a DNA template. Here's a breakdown:
- Initiation: RNA polymerase, an enzyme, binds to a specific region of the DNA called the promoter. This signals the start of transcription.
- Elongation: RNA polymerase unwinds the DNA double helix and moves along the template strand, synthesizing a complementary mRNA molecule. Instead of thymine (T), uracil (U) is used in the mRNA sequence.
- Termination: The RNA polymerase reaches a termination sequence on the DNA, signaling the end of transcription. The newly synthesized mRNA molecule is released.
The mRNA molecule then undergoes processing (in eukaryotes) before it can be translated into a protein. This processing includes:
- Capping: A modified guanine nucleotide is added to the 5' end of the mRNA, protecting it from degradation.
- Splicing: Non-coding regions of the mRNA called introns are removed, and the coding regions (exons) are joined together.
- Polyadenylation: A poly(A) tail (a string of adenine nucleotides) is added to the 3' end, further protecting the mRNA from degradation and aiding in its export from the nucleus.
Translation: RNA to Protein
Translation is the second step, where the mRNA sequence is used to synthesize a polypeptide chain (which folds into a functional protein). This occurs in the ribosomes, cellular structures composed of ribosomal RNA (rRNA) and proteins.
- Initiation: The ribosome binds to the mRNA molecule at the start codon (AUG). A transfer RNA (tRNA) molecule carrying the amino acid methionine binds to the start codon.
- Elongation: The ribosome moves along the mRNA molecule, reading the codons (three-nucleotide sequences) one by one. Each codon specifies a particular amino acid. tRNA molecules carrying the corresponding amino acids bind to the codons, and peptide bonds are formed between the amino acids, creating a growing polypeptide chain.
- Termination: The ribosome reaches a stop codon (UAA, UAG, or UGA), signaling the end of translation. The polypeptide chain is released from the ribosome and folds into a functional protein.
In summary, the process of converting DNA to protein is accurately named transcription and translation. Transcription creates an mRNA copy of the DNA sequence, while translation uses this mRNA sequence to build a polypeptide chain that folds into a protein. This intricate process is crucial for cellular function and the expression of genetic information.
