ch 13 translation of mrna Flashcards
translation
the process in which the sequence of codons within mrna provides the information to synthesize the sequence of amino acids that constitute a polypeptide
protein-encoding genes
(also called structural genes) genes that produce mrna and encode polypeptides
messenger rna
(also called mRNA) a type of rna that is transcribe from a protein-encoding gene and contains the information for the synthesis of a polypeptide
alkaptonuria
a human genetic disorder involving the accumulation of homogentisic acid in the body due to a lack of the enzyme homogentisic acid oxidase
inborn error of metabolism
a genetic disease that involves a defect in a metabolic enzyme
one-gene/one-enzyme hypothesis
the idea, which later needed to be expanded, that one gene encodes one enzyme
polypeptide
a linear sequence of amino acids that is the produce of mrna translation; one or more polypeptides fold and associate with each other to form a functional protein
protein
a functional unit composed of one or more polypeptides
genetic code
the correspondence between a codon (a sequence of three bases in an mrna molecule) and the functional role that the codon plays during translation; each codon specifies a particular amino acid or the end of translation
sense codon
a codon that encodes a specific amino acid
start codon
a three base sequence in mrna that initiates translation; it is usually 5’–AUG–3’ and encodes methionine
stop codon
(also called termination codon or nonsense codon) a three base sequence in mrna that signals the end of translation of a polypeptide; the three stop codons are 5’–UAA–3’, 5’–UAG–3’, and 5’–UGA–3’
5’ -untranslated region
in an mrna, the region at the 5’ end that precedes te codons that are translated into an amino acid sequence within a poly peptide
3’ - untranslated region
- in an mrna, the region at the 3’ end that follows the codons that are translated into an amino acid sequence within a polypeptide unit
- the region of an mrna that is downstream from a stop codon
anticodon
a three nucleotide sequence in trna that is complementary to a codon in mrna
degeneracy
in genetics, this term means that more than one codon specifies the same amino acid; for example, the codons GGU, GGC, GGA, and GGG all specify the amino acid glycine
synonymous codons
two or more different codons that specify the same amino acid
reading frame
a series of codons determined by reading bases in groups of three beginning with the start codon as a frame of reference
selenocysteine
a nonstandard amino acid that maybe incorporated into polypeptides during translation
pyrrolysine
a nonstandard amino acid that maybe incorporated into polypeptides during translation
peptide bond
a covalent bond formed between the carboxyl group in one amino acid in a polypeptide and the amino group in the next amino acid
amino-terminus
(also called n-terminus and amino terminal end) the location of the first amino acid in a polypeptide; the amino acid at the amino-terminus retains a free amino group that is not covalently attached to the second amino acid
carboxyl-terminus
(also called c-terminus) the location of the last amino acid in a polypeptide chain; the amino acid at the c-terminus retains a free carboxyl group that is not covalently attached to another amino acid
side chain
(also called r-group) in an amino acid, the chemical structure attached to the carbon atom (ie the ⍺ carbon) that is located between the amino and carboxyl groups
primary structure
with regard to proteins, the linear sequence of amino acids that forms a polypeptide
chaperone
a protein that aids in the folding of polypeptides
secondary structure
a regular repeating pattern of molecular structure, such as the dna double helix or the ⍺ helix and β sheet found in proteins
⍺ helix
a type of secondary structure found in proteins
β sheet
a type of secondary structure found in proteins
tertiary structure
the 3d structure of a macromolecule, such as the tertiary structure of a polypeptide
quaternary structure
the structure of a functional protein formed when two or more polypeptides associate with each other
subunit
a component of a larger complex; in a protein, each subunit is a single polypeptide
cell-free translation system
an experimental mixture that can synthesize polypeptides
adaptor hypothesis
a hypothesis that proposes a trna has two functions:
- recognizing a three base codon sequence in mrna
- carrying an amino acid that is specific for that codon
aminoacyl-tRNA synthetase
an enzyme that catalyzes the attachment of a specific amino acid to the correct trna
charged tRNA
(also called aminoacyl-tRNA) a trna that has an amino acid attached to its 3’ end by a covalent bond
wobble rules
rules that govern the binding specificity between the third base in a codon and the first base in an anticodon
isoacceptor tRNAs
two or more trnas that differ at the wobble position but can recognixe the same codon
ribosome
a large macromolecular structure that acts as the catalytic site for polypeptide synthesis; the ribosome allows the mrna and trnas to be positioned correctly as the polypeptide is made
nucleolus
an organelle within the nucleus of eukaryotic cells where the assembly of ribosomal subunit occurs
polyribosome
(also called polysome) an mrna transcript that has many bound ribosomes in the act of translation
peptidyl site
(also called P site) a site onf a ribosome that carries a trna along with a polypeptide
aminoacyl site
(also called A site) a site on a ribosome where a charged trna initially binds
initiation
in translation, the formation of a complex between mrna, the initiator trna, and the ribosomal subunits
exit site
(also called E site) a site on a ribosome where an uncharged trna binds and then is released
elongation
in translation, the synthesis of a polypeptide using the information within mrna
termination
in translation, the release of the polypeptide and the last trna and the disassemblt of the ribosomal subunits and mrna
initiator tRNA
during translation, the trna that recognizes the start codon in the mrna
shine-dalgarno sequence
(also known as ribosome-binding site) a short sequence in bacterial mrna that binds to a ribosome and initiates translation
kozak’s rules
a set of rules that identify the most favorable types of bases to flank a eukaryotic start codon in an mrna molecule
decoding function
the ability of 16S rrna to detect when an incorrect trna is bound at the A site and prevent elongation until the mispaired trna is released from the A site
peptidyl transfer
the step during the elongation stage of translation in which the polypeptide is removed from the trna in the p site and transferred to the amino acid at the A site
peptidyl transferase
a complex that functions during translation to catalyze the formation of a peptide bond between the amino acid in the A site of the ribosome and the growing polypeptide
release factor
a protein that recognizes a stop codon and promotes termination of translation and the release of the completed polypeptide
antibiotic
any substance produced by a microorganism that inhibits the growth of other microorganisms, such as pathogenic bacteria
