Bio (Protein synthesis)

protein synthesis

process by which proteins are made (turning DNA into functional protein)

proteins

large biological molecules made up of one or more amino acid chains

protein synthesis steps and which one comes first

translation and transcription, transcription comes first

purpose of transcription

to produce a mRNA molecule from the DNA in the nucleus so DNA doesn’t get damaged leaving the nucleus

translation

the process of decoding genetic information in mRNA into a specific amino acid chain

triplet

a sequence of three bases along a DNA molecule

codon

a sequence of three consecutive bases on a mRNA molecule. a codon is complementary to a triplet on DNA

first step of transcription

initiation: RNA polymerase binds to the promoter sequence of the gene. It unwinds the DNA double helix so the gene can be copied.

second step of transcription

elongation: RNA polymerase moves along the DNA template strand. It adds RNA nucleotides one at a time using complementary base pairing.

third step of transcription

termination: RNA polymerase reaches the termination sequence. RNA polymerase and the mRNA detach from the DNA.

what happens after the step of termination in transcription

introns are spliced out and exons and expressed. A 5′ cap and 3′ polytail are added to protect the mRNA. DNA rewinds back up.

first step of translation

initiation: The mRNA is in the cytoplasm. A ribosome attaches to the start codon (AUG) on the mRNA. A tRNA with the matching anticodon brings the first amino acid, methionine (Met).

second step of translation

elongation: The ribosome moves along the mRNA, reading one codon at a time. tRNAs bring the correct amino acids and amino acids join together with peptide bonds. This creates a growing polypeptide chain.

third step of translation

termination: Ribosome reaches a stop sequence: UGA, UAA, UAG. The polypeptide chain is released and folds into a functional protein.

anticodon

sequence of three consecutive bases on a tRNA molecule

difference in function of DNA and mRNA

DNA stores the permanent genetic information for an organism and mRNA is a temporary copy of genetic information and carries it to the ribosome