Chapter 15: The Genetic Code and Translation

mutants will live when supplemented with the amino acid they lack

how do we know that genes encode proteins?

one gene one enzyme hypothesis

each gene specifically codes for the production of a single, unique enzyme, controlling one step in a metabolic pathway

one gene, one polypeptide hypothesis

each gene encodes the information necessary to produce a single polypeptide chain

they have many functions

why do proteins matter?

radical group

what gives amino acids their uniqueness?

domain

regions within a primary structure that can have characteristic traits at higher structures; ex: transformation factor has DNA binding proteins

codon

the set of nucleotides that encode a single amino acid

sense codon

sequences of three nucleotides in DNA or mRNA that specify one of the 20 amino acids used in protein synthesis

synonymous codons

codons that specify the same amino acid

reading frame

one of three possible ways to read a nucleotide sequence (DNA or RNA) in non-overlapping, three-nucleotide units called codons

start codon

codon that signals for protein synthesis to begin; AUG

stop codon

codon that signals for the termination of protein synthesis; UAG, UGA, and UAA

bring amino acids to the ribosome

what do tRNAs do?

wobble

the third base of a codon (5'-to-3') can bind flexibly with the first base of a tRNA anticodon

amino end

where does protein synthesis begin?

ribosome

mobile protein-synthesizing machines

tRNA charging, initiation, elongation, and termination

what are the stages of translation?

tRNA charging

joining of the tRNA with the appropriate amino acid

aminoacyl-tRNA synthetsases

recognize their amino acids by size, charge, and R group

70S initiation complex

the functional, assembled ribosome in bacteria that initiates protein synthesis

Kozak sequence

short nucleotide sequence surrounding the start codon that indicates where its located

elongation factor

specialized proteins that bind to RNA polymerase II (RNAPII), facilitating the synthesis of RNA by promoting rapid, continuous movement along DNA

termination

ribosome translates to a stop codon and release factors can bind to the stop codon; polypeptide is released and tRNA, mRNA, and release factors are released

polyribosome

an mRNA with multiple ribosomes attached

prokaryotes

are polyribosomes located in prokaryotes or eukaryotes?

molecular chaperones

specialized proteins that assist in the correct folding, assembly, and transport of other macromolecules