Ribosomes and Protein Synthesis

Polypeptides

the name for a long chain of amino acids

Genetic Code

collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis; the bases in RNA that form a "language" from four letters A, C, G, U

Codon

a group of three consecutive nucleotide bases in messenger RNA that specifies a particular amino acid to be incorporated onto a protein, read by tRNA

Translation

the decoding process of the sequence of bases in mRNA message into a sequence of amino acids making up a protein, ribosomes using the sequence of codons in mRNA to assemble amino acids into polypeptide chains

Steps of translation

1) ribosome attaches to an mRNA molecule in cytoplasm
2) each codon passes through ribosome, tRNAs bring proper amino acids (anticodons) into ribosome
3) ribosome attaches amino acids into a growing chain
4) ribosome has second binding sit for next tRNA m

Anticodon

Three unpaired bases on tRNA molecule, complementary to one mRNA codon

Central Dogma of Molecular Biology

Information is transferred from DNA to RNA to protein (many exceptions, such as viruses transferring in opposite direction from RNA to DNA), useful generalization

Gene Expression

Process by which a gene produces its product and the product carries out its function

Start Codon

Methionine codon AUG, initiates protein synthesis

Stop Codon

Ends translation, 3 stop codons exist

Sequence of nucleotide bases in an mRNA Molecule

Set of instructions that gives the order in which amino acids should be joined to produce a polypeptide

In translation, ribosomes...

Use the sequence of codons in mRNA to assemble amino acids into polypeptide chains

Roles of tRNA, rRNA and mRNA in translation

mRNA- carries coded message that directs the process
tRNA- delivers exactly the right amino acid called for by each codon on the mRNA (adaptors that enable the ribosome to 'read' mRNA messages and get them right)
rRNA- ribosomes are composed of 3 or 4 of