Translation and the Genetic Code Regular

Flashcards covering Translation of mRNA, genes and enzymes, Beadle and Tatum's experiments, the genetic code, tRNA, and ribosome structure.

Translation

The process where the nucleotide language of mRNA is translated into the amino acid language of proteins.

Alkaptonuria

An inherited disease where patients lack a particular enzyme.

Archibald Garrod

Proposed that alkaptonuria was due to a missing enzyme, namely homogentisic acid oxidase, and described the disease as an inborn error of metabolism.

One Gene-One Enzyme Hypothesis

States that a single gene controls the synthesis of a single enzyme; has been modified to one-gene/one-polypeptide hypothesis.

One Gene-One Polypeptide Hypothesis

States that a protein-coding gene codes a polypeptide.

Codons

Groups of three nucleotides within mRNA that contain genetic information.

AUG

The start codon, which specifies methionine and defines the reading frame.

UAA, UAG, UGA

Termination codons that signal the end of translation.

Degeneracy

The concept that more than one codon can specify the same amino acid.

Synonymous Codons

Codons that specify the same amino acid.

21st and 22nd amino acids

Selenocysteine (Sec) and pyrrolysine (Pyl)

Reading Frame

A series of codons beginning with the start codon.

N-terminus

The end of a polypeptide chain with an exposed amino group.

C-terminus

The end of a polypeptide chain with an exposed carboxyl group.

Primary Structure

The amino acid sequence of a protein.

Secondary Structures

Regular, repeating shapes within a protein, such as α helix and β sheet.

Tertiary Structure

The final three-dimensional conformation of a protein composed of a single polypeptide

Quaternary Structure

Formed when two or more polypeptides associate with one another to make a functional protein

Marshall Nirenberg

Used synthetic RNA to decipher the relationship between base composition and particular amino acids.

Polynucleotide Phosphorylase

Enzyme used to catalyze the covalent linkage of ribonucleotides into RNA to make synthetic RNA.

H. Gobind Khorana

Short RNAs (2 to 4 nucleotides long) that had a defined sequence. Used to synthesize RNA.

Triplet-Binding Assay

3 nucleotide RNA could cause a ribosome to bind a tRNA

tRNAs

Play a direct role in the recognition of codons in mRNA

Adaptor Hypothesis

A hypothesis that tRNA has two functions: recognizing a 3-base codon in mRNA and carrying an amino acid that is specific for that codon.

Anticodon

The specific sequence in tRNA that binds to a complementary codon in mRNA.

Aminoacyl-tRNA Synthetases

Enzymes that attach amino acids to tRNAs.

Charged tRNA (Aminoacyl-tRNA)

A tRNA with an amino acid attached to its 3’ end.

Wobble Hypothesis

The concept that third position in the codon-anticodon recognition process can “wobble” or move a bit, tolerating certain mismatches

Isoacceptor tRNAs

tRNAs that are able to recognize the same codon.

Ribosome

A large macromolecular complex where translation occurs.

Polyribosome (Polysome)

An mRNA transcript that has many bound ribosomes during translation.

Ribosomes three discrete sites

Peptidyl site , Aminoacyl site, Exit site

Initiation Complex

The mRNA, initiator tRNA, and ribosomal subunits associate to form

Shine-Dalgarno Sequence

Located on mRNA, this is complementary to a sequence in the 16S rRNA which helps the binding of mRNA to the 30S subunit

Kozak’s Rules

Rules for optimal translation initiations

Peptidyl Transfer

The polypeptide is removed from the tRNA in the P site and transferred to the amino acid at the A site during elongation

Translocation

During elongation, the ribosome moves to the next codon in the mRNA, moving the tRNAs at the P and A sites to the E and P sites

RF1

Recognizes UAA and UAG

RF2

Recognizes UAA and UGA

RF3

Does not recognize any of the three codons - required for the termination process

Coupling

When translation begins before transcription ends

Antibiotics

Prevents bacterial growth without harming the eukaryotic cell