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Protein synthesis consists of two main processes: transcription and translation.
Proteins are essential for life, playing roles in reproduction, growth, repair, and metabolic regulation.

Definition: Transcription is the process of using DNA as a template to synthesize RNA.
- In eukaryotes, transcription occurs in the nucleus.
- In prokaryotes, transcription occurs in the cytoplasm.
Three Main Steps:
- Initiation: All necessary components assemble at the promoter region of the gene.
- Elongation: RNA polymerase synthesizes RNA by reading the DNA template strand.
- Termination: RNA polymerase reaches a terminator sequence, releasing the RNA molecule.

RNA Polymerase: The enzyme responsible for synthesizing RNA from the DNA template.
Promoter: The region where RNA polymerase binds to DNA to initiate transcription.
Transcription Bubble: The region where the DNA strands have unwound and unzipped during transcription.
Template Strand: The DNA strand that RNA polymerase uses as a template to construct the RNA molecule.
RNA synthesis follows complementary base pairing:
- Adenine (A) on DNA pairs with Uracil (U) on RNA (no Thymine in RNA).
- A – U and C – G base pairing occur during transcription.
After synthesis, RNA tails off and DNA rewinds into its double helix structure.

Eukaryotic RNA requires processing (involves splicing, capping, and tailing) before it can be translated, while prokaryotic RNA is directly translated as produced.
Prokaryotes can simultaneously perform transcription and translation, as both processes occur in the cytoplasm.

Messenger RNA (mRNA): Carries genetic information from DNA to the ribosome.
Transfer RNA (tRNA): Transfers specific amino acids to the growing polypeptide chain during translation.
Ribosomal RNA (rRNA): Structural and functional components of the ribosome, vital for protein synthesis.

mRNA is read in groups of three bases called codons, with each codon corresponding to a specific amino acid.
For example, AUG is the start codon, while UAA, UAG, and UGA are stop codons.

Initiation: mRNA, ribosomal subunits, and tRNA come together to form the initiation complex.
The start codon (AUG) on mRNA binds to tRNA with the complementary anticodon (UAC), bringing in methionine.

An incoming tRNA with an anticodon complementary to the next mRNA codon adds its amino acid to the growing polypeptide chain, forming a peptide bond.
The ribosome moves along the mRNA, facilitating the addition of amino acids until a stop codon is reached.

Occurs when a stop codon is encountered, resulting in the release of the newly synthesized polypeptide chain.
The completed polypeptide will undergo further processing to become a functional protein.

Point Mutations: Affect a single base pair.
- Missense Mutation: Causes a different amino acid to be incorporated into the protein.
- Nonsense Mutation: Introduces a premature stop codon, truncating the protein.
- Silent Mutation: Results in no change to the amino acid sequence despite a nucleotide change.
Frameshift Mutations: Caused by insertions or deletions, affecting multiple base pairs and altering the reading frame.

Spontaneous Mutations: Result from errors in DNA replication.
Induced Mutations: Caused by external factors (mutagens) like chemicals or radiation, increasing mutation rates.

Protein synthesis is a complex and vital process, essential to life, allowing organisms to create the proteins necessary for their structure and functions.