Translation, Genetic Code, and Mutations Flashcards

Vocabulary flashcards covering the properties of the genetic code, start/stop codons, codon-anticodon recognition, wobble hypothesis, types of point and frameshift mutations, and associated genetic diseases based on Prof. Said Oraby's lecture notes.

Genetic Code

The sequence of nucleotides in DNA and mRNA that determines the amino acid sequence in proteins during protein synthesis.

Codon

A 3-nucleotide sequence in mRNA that specifies a particular amino acid or a stop signal, always read in the 5' to 3' direction.

Start Codon

The codon AUG, which codes for Methionine and ensures the correct initiation of translation.

Stop Codons

Nonsense codons (UAA, UAG, UGA) that do not code for any amino acid and signal the termination of protein synthesis.

Degeneracy (Redundancy)

A characteristic of the genetic code where multiple codons can code for the exact same amino acid.

Non-overlapping

A feature of the genetic code in which each base in a DNA or RNA sequence belongs to only one codon.

Commaless

A property of the genetic code meaning there are no gaps or spaces between adjacent codons.

Unambiguous

A property of the genetic code where each specific codon codes for only 1 amino acid.

Universal

A property indicating that the genetic code is identical in nearly all organisms, with very few exceptions like mitochondria.

Wobble Hypothesis

The concept that the 5' base of a tRNA anticodon can pair flexibly with multiple bases at the 3' codon position, reducing the required number of unique tRNAs and explaining genetic code degeneracy.

Mutation

A change in the nucleotide sequence of the genetic code that can alter protein structure/function and cause genetic disease.

Point Mutation

A single base substitution mutation in a DNA sequence.

Transition Mutation

A point mutation in which a purine is replaced by another purine, or a pyrimidine by another pyrimidine.

Transversion Mutation

A point mutation in which a purine is replaced by a pyrimidine, or vice versa.

Silent Mutation

A point mutation that changes a codon sequence without changing the encoded amino acid, having no effect on the protein.

Missense Mutation

A point mutation resulting in a codon change that substitutes one amino acid for another in the protein sequence.

Nonsense Mutation

A point mutation that converts an amino acid codon into a premature stop codon, producing a shortened, nonfunctional protein.

Sickle Cell Anemia

A disease caused by a point, transversion, missense mutation in the $\beta$-globin gene (GAG to GTG) replacing glutamate with valine at position 6, forming abnormal HbS and fragile red blood cells.

Frameshift Mutation

A mutation caused by insertion or deletion of nucleotide(s) that alters the downstream reading frame of mRNA.

CFTR

Cystic Fibrosis Transmembrane Conductance Regulator; a protein channel that moves chloride ions to the outside of cells.

Cystic Fibrosis

An autosomal recessive frameshift disorder caused by deletion of 3 nucleotides in the CFTR gene (losing Phe508), resulting in a defective chloride channel and thick mucus buildup.

Trinucleotide Repeat Expansion

A mutation characterized by abnormal repetition of 3-base sequences (e.g., CAG, CGG, GAA), producing extra amino acids and toxic protein aggregates.

Huntington Disease

A condition caused by a CAG trinucleotide repeat expansion producing toxic huntingtin protein, leading to brain ventricle enlargement and atrophy of cerebral nerve tissue and basal ganglia.

Splice Site Mutation

A mutation that affects pre-mRNA splicing, leading to skipped exons or retained introns and producing abnormal, nonfunctional proteins.

Myotonic Dystrophy

A disease caused by a splice site mutation that leads to progressive muscle wasting and weakness.