MCB 110: Protein Synthesis and the Genetic Code

Flashcards covering the fundamentals of protein synthesis, RNA/DNA structure, genetic code characteristics, tRNA anatomy, and mutation types based on MCB 110 lecture notes.

Transcription

The process of copying the DNA sequence of a region of the genome into an RNA molecule.

Translation

The process of using information in RNA to direct the manufacture of a particular protein.

RNA chemical reactivity

The additional $2'$ oxygen in the RNA ribose makes it more chemically reactive than DNA and enables it to form more complex 3D structures.

Purines

A category of nitrogenous bases that includes adenine (A) and guanine (G).

Pyrimidines

A category of nitrogenous bases that includes cytosine (C), thymine (T) [found only in DNA], and uracil (U) [found only in RNA].

Triplet Code

The simplest code that can specify all 20 amino acids; three nucleotide bases provide $4^3 = 64$ different outputs.

Sense codon

A triplet codon that specifies a single amino acid.

Nonsense codon

Also known as a stop codon; it specifies no amino acid and signals the end of the protein-coding region of the mRNA.

Messenger RNAs (mRNAs)

Coding RNAs that contain the information needed to produce a protein.

Transfer RNAs (tRNAs)

Molecules that read the mRNA by base-pairing 3 nucleotides (anticodon) with the mRNA codon to interpret information into a protein sequence.

Decoding

The process where tRNA base-pairs its anticodon with the codon on the mRNA.

Nascent chain

The chain of amino acids attached to tRNAs as they are joined together during translation.

Ribosome

A large molecular machine composed of protein and RNA components that performs translation.

A-form helix

The form taken by most RNA and RNA-DNA duplexes; it is shorter and wider than the B-form due to steric hindrance.

Acceptor stem

The region of tRNA formed by base-pairing the $5'$ and $3'$ ends, featuring a conserved $3'$ CCA tail that binds the amino acid.

Anticodon loop

A loop in tRNA containing three nucleotides that base-pair with the codon in mRNA.

Inosine (I)

A modified base in tRNAs converted by tRNA-specific adenosine deaminase that can pair with U, C, or A.

Hypermodified purine (H)

A modified base located after the anticodon that prevents its base-pairing and helps align the codon and anticodon properly.

Isoacceptors

Different tRNAs that carry the same amino acids.

Wobble pairing

Allowed pairing deviations at the third position of the codon and position 1 of the anticodon, such as G-U or Inosine-U/C/A.

Missense mutation

A single nucleotide change that alters the encoded amino acid.

Nonsense mutation

A single nucleotide change that introduces a premature stop codon.

Silent mutation

A single nucleotide change that does not alter the encoded amino acid.

Rare codons

Codons used more infrequently than others, which tend to be decoded by rare tRNAs.