13.2: The Genetic Code

genetic code

informational key in which mRNA sequence can be translated into sequence of amino acids to create the protein expressed by the gene

codon

triplet code - sequence of 3 nucleotides in mRNA that specifies a single amino acid in protein

why is genetic code redundant but not ambiguous

multiple codons code for the same amino acid. not ambiguous because each codon codes for only specific amino acid

start codon

AUG - signals the beginning of translation - codes for methionine.

stop codon

UAA, UAG, and UGA - signals termination of protein synthesis

structure of tRNA

Di typical secondary structure with an anticodon that’s complementary to mRNA codon

• 3’ end where amino acids attach - each tRNA carries a specific amino acid that corresponds to anticodon = when attached tRNA is charged

• no tRNA corresponds to any stop codons

open reading frame

region of DNA sequence that can be translated into a protein - continuous sequence of codons starting with a start codon and ending with stop codon