13.2 - The Genetic Code and Translation

The Genetic Code mRNA carries the information for a specific protein written as a series of 3 bases called codons

a codon “codes for” the amino acid an amino acid may have more than one codon because there are 64 possible codons are different codon charts used to find the appropriate amino acid

one codon - AUG (Methionine) - is called the “start codon” this tells the ribosome to begin making a protein Three other codons are called “stop codons” these tell the ribosome to stop adding amino acids to the chain because the protein is complete

use the code by reading from the center to the outside example: AUG codes for Methionine (start codon)

use the code by reading letters from left to right example: AUG codes for Methionine (start codon)

Name the Amino Acids GGG? UCA? CAU? GCA? AAA?

Translation process of decoding the mRNA into a protein takes place in the cytoplasm at the ribosomes ribosomes are site of protein synthesis

ribosomal RNA (rRNA), along with protein, makes up the ribosomes rRNA is a globular shape

transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized (made) transfer RNA (tRNA) is clover-leaf shape

each tRNA molecule has an attachment site at one end for a specific amino acid opposite end has three nucleotide bases called the anticodon anticodon in a tRNA is complementary to the 3 bases of a specific codon

Transfer RNA amino acid attachment site U A C anticodon

Remember the Complementary Bases for DNA: C-G A-T for RNA: A-U 13

example: codon (mRNA) = ACU amino acid coded for = threonine anticodon (tRNA) = UGA threonine U G A A C U

mRNA attaches itself to one end of a ribosome ribosome then moves along mRNA strand to “read” the code brought from the DNA ribosome will put together the amino acids into a polypeptide chain that makes up the protein

Once it reaches the “stop codon” the ribosome will release the protein into the cell.