Protein Translation Chapter

Study Notes

The central dogma of molecular biology: DNA → RNA → Polypeptide.
Amino acids have a simple backbone structure consisting of an amino group, a carboxyl group, and a side chain (R group).
Four levels of protein structure: primary, secondary, tertiary, and quaternary.

Primary Structure: Sequence of amino acids in a polypeptide chain.
Secondary Structure: Local folding of the polypeptide into alpha helices and beta sheets through hydrogen bonding.
Tertiary Structure: Overall 3D shape formed by interactions among side chains (R groups).
Quaternary Structure: Assembly of multiple polypeptide chains into a functional complex.

Codon: A sequence of three nucleotides in mRNA that specifies an amino acid.
Degenerate: Multiple codons can code for the same amino acid.
Universal: Genetic code is conserved across all forms of life, indicating common ancestry.
Importance of a three-letter code allows for 64 possible combinations, far exceeding the number of amino acids.

Initiation requires large and small ribosomal subunits, mRNA, tRNA (transfer RNA) with amino acids, and initiation factors.
mRNA is read in triplets (codons), ensuring a non-overlapping reading frame.
Reading Frame: The way nucleotides are grouped into codons; shifting it alters the entire sequence.

Each amino acid is linked to a specific tRNA, forming a "charged" tRNA.
tRNA pairs with the mRNA codon, facilitating the translation of nucleic acid to amino acid.

Bacteria lack a nucleus, allowing transcription and translation to occur simultaneously.
Eukaryotic translation requires processing of mRNA (e.g., capping and polyadenylation) before it can be translated.

Missense Mutation: Changes one amino acid, potentially altering protein function.
Nonsense Mutation: Creates a premature stop codon, truncating the protein.
Silent Mutation: Changes a nucleotide without affecting the amino acid sequence.
Frameshift Mutation: Addition or deletion of nucleotides shifts the reading frame, impacting all downstream codons.

Single base changes can result in various mutation types, affecting protein products significantly.
Mutations may occur in coding or non-coding sequences, affecting gene regulation and expression.
Mutations in somatic cells affect individual organisms; those in germ cells can be inherited.

DNA identified as hereditary material through key experiments.
Bacteria reproduce asexually but can exchange DNA through various mechanisms.
DNA and RNA structure features (complementary bases, antiparallel strands) are crucial for understanding replication and transcription.
The semiconservative model best explains DNA replication.
Modifications to RNA transcripts are common before they become functional.
Translation involves key roles for tRNA and rRNA to synthesize polypeptides from mRNA.