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Transcription and Translation

Introduction​

Transcription and translation are fundamental processes in molecular biology that form the basis of gene expression. These two processes work together to convert genetic information from DNA into proteins, which are essential for various cellular functions.

In this article, we will explore both transcription and translation in detail, providing explanations, examples, and illustrations to help students understand these complex biological processes.

What is Transcription?​

Transcription is the process by which a segment of DNA is copied into a complementary RNA molecule. This process occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells.

Key Points of Transcription​

  1. Initiation: The process begins when an enzyme called RNA polymerase binds to a specific region of the DNA called the promoter.

  2. Elongation: As RNA polymerase moves along the DNA template, it adds nucleotides to the growing RNA chain.

  3. Termination: When the RNA polymerase reaches the end of the gene, it releases the newly formed RNA molecule.

Types of RNA Produced During Transcription​

There are three main types of RNA produced during transcription:

  1. Messenger RNA (mRNA): Carries genetic information from DNA to the ribosome for protein synthesis.

  2. Transfer RNA (tRNA): Brings amino acids to the ribosome during protein synthesis.

  3. Ribosomal RNA (rRNA): Forms part of the ribosomes themselves.

What is Translation?​

Translation is the process by which the genetic information encoded in an mRNA molecule is converted into a sequence of amino acids, forming a polypeptide chain.

Key Points of Translation​

  1. Initiation: The process begins when a small subunit of the ribosome binds to the mRNA and recruits the first tRNA carrying methionine (the start codon).

  2. Elongation: As the ribosome moves along the mRNA, it reads the codons and matches them to the corresponding amino acids brought by tRNAs.

  3. Termination: When the ribosome reaches a stop codon, it releases the newly formed polypeptide chain.

The Genetic Code​

The genetic code is a set of rules used by living cells to translate information encoded within genetic material (DNA or RNA sequences) into proteins. Each codon codes for a specific amino acid or stop signal.

Here's a simplified version of the genetic code table:

CodonAmino Acid
AUGMethionine
UUU/UUCPhenylalanine
UUA/UUGLeucine
......

Examples of Transcription and Translation​

Let's look at a simple example of transcription and translation using the gene for the enzyme beta-galactosidase:

Transcription Example​