Protein Synthesis

Cells need to build proteins. Thus, they need protein plans. They do this through transcription and translation.

How to build protein? DNA →mRNA → MRNA → Protein

Transcription: “writing”

This occurs in the nucleus.

• Initiation: mRNA polymerase finds a promoter and binds to it

• Elongation: transcription begins, and the polymerase moves down, creating RNA

• Termination: transcription stops at the termination point

Translation, “reading”

This occurs in the ribosome in the cytoplasm. The ribosome reads mRNA via codons, 3-letter codes made of the letters A, U, C, and G. 3 letters equate to an amino acid, codon third letter is sometimes not important.

Remember, U replaces T in RNA.

tRNA matches the codons with anticodons, the matching opposites to the codons. For example, AUG is the start codon; UAC is the anticodon. Amino acids join by peptide bonds.

There are 3 types of RNA:

• mRNA (messenger), which is the gene copy

• tRNA (transfer), which is how the amino acids get into the ribosome

• rRNA (ribosomal), in ribosome catalytic activity and structure

20 amino acids make all the proteins

Deeper into the ribosome process

tRNA and mRNA get together, matching codon to anticodon. They link amino acids until the stop codon is reached.