Part 2~Bio (Transcription and Translation )

Central Dogma

The flow of genetic information summarized as: DNA → RNA → Protein

Transcription

The process where DNA is used as a template to synthesize RNA. Occurs in the nucleus for Eukaryotes and cytoplasm for Prokaryotes.

Initiation (Transcription)

Recognition of the promoter sequence by RNA polymerase, starting transcription.

Elongation (Transcription)

RNA polymerase synthesizes RNA by reading the DNA strand in a 3′ to 5′ direction, resulting in RNA synthesis in the 5′ to 3′ direction.

Termination (Transcription)

Occurs when RNA polymerase reaches a terminator sequence on the DNA, signaling the end of transcription.

Promoter

A specific DNA sequence that serves as the binding site for RNA polymerase, initiating transcription.

Terminator

A specific DNA sequence that signals the end of transcription.

Eukaryotic mRNA Processing

Modifications to the primary RNA transcript in eukaryotes, including addition of a 5′ cap, a poly-A tail, and splicing (removal of introns).

5′ cap

An addition to the 5' end of eukaryotic mRNA to protect it from degradation.

Poly-A tail

An addition at the 3' end of eukaryotic mRNA for stability and export from the nucleus.

Splicing

The removal of non-coding sequences (introns) from eukaryotic mRNA, leaving only coding sequences (exons).

Introns

Non-coding sequences within a gene that are removed during RNA processing in eukaryotes.

Exons

Coding regions within a gene that are translated into proteins after introns are removed during RNA processing.

Translation

The process where ribosomes read mRNA in a 5′ to 3′ direction, decoding codons into a polypeptide chain (protein).

Codons

Units of three nucleotides on mRNA that are read by ribosomes; each codon pairs with a specific tRNA anticodon carrying an amino acid.

Start Codon

AUG, which codes for Methionine and initiates translation.

Stop Codons

Three codons (UAA, UAG, UGA) that signal the termination of translation.

Initiation (Translation)

Begins with the recognition of the start codon by the ribosome.

Elongation (Translation)

tRNA molecules carry amino acids and form peptide bonds between them, lengthening the polypeptide chain.

Termination (Translation)

Concludes when a stop codon is reached, releasing the newly synthesized polypeptide chain.

tRNA Function

tRNA molecules decode the mRNA sequence to form a polypeptide chain, ultimately resulting in protein synthesis, by carrying specific amino acids to the ribosome based on anticodon-codon pairing.