L12 translation

Flashcards covering key vocabulary and concepts from the lecture on gene expression and translation.

Genetic Code

A set of rules by which information encoded in DNA or mRNA sequences is translated into proteins.

Translation

synthesis of proteins by ribosomes using mRNA as a set of instructions.

Codon (triplet)

A sequence of three nucleotides in mRNA that corresponds to a specific amino acid.

AUG

codon that specifies start, and methionine (for synthesising protien)

3 codons that specify stop

UAA, UAG, UGA

Key features of genetic code

most amino acids have more than one codon, 61 out of 64 codons specify an amino acid

tRNA (Transfer RNA)

A type of RNA that carries amino acids to the ribosome for protein synthesis and contains an anticodon complementary to the mRNA codon.

tRNA structurally important features

Amino acid attachment site, anticodon (needs UUC to pair with anti-parallel)

charged tRNA

tRNA that has been joined to corrisponding amino acid by aminoacyl-tRNA synthatase.

Steps to charge tRNA

Enzyme aminoacyl-tRNA synthetase recognises specific amino acid and the correct tRNA and joins them togethere. There are 20 different enzymes for the 20 amino acids.

Aminoacyl-tRNA Synthetase

An enzyme that attaches the appropriate amino acid to its corresponding tRNA.

Ribosome

A molecular machine that synthesizes proteins by translating mRNA into amino acid sequences. Made up of a small and large subunit.

Initiation

Initiation tRNA-met (start codon) binds to small ribosomal subunit , identifies 5’ G cap and attatches to mRNA. It then moves along mRNA (5’-3’) until it finds initiation AUG codon. Complex stops, initiator tRNA-met stops in the p site. Large ribosomal subunit arrives, initiation complex is complete.

Elongation

Charged tRNA enters the A site (codon recognition), the polypeptide chain binds to the new amino acid (peptide bond formation). Then the ribosome moves 3 nucleotides down the mRNA, uncharged tRNA moves to the exit side and is released, tRNA with polypeptide chain moves to the p site (translocation)

Termination

When a stop codon is reached, release factor enters A site. Which breaks the bond between P site tRNA (using water) and the final amino acid. Polypeptide detatches from tRNA and is released.

Genotype and phenotype relation to DOGMA

Variation in genotype (DNA level) is often reflected as variation in phenotype (protein level)