Amino Acids & Proteins
Amino group, carboxyl group, hydrogen, and R group (side chain)
What are the four parts of a basic amino acid structure?
mRNA
What molecule carries the code from DNA to ribosomes?
What is the purpose of gene regulation?
To control when, where, and how much a gene is expressed.
Where does transcription and translation occur in prokaryotes?
Both occur in the cytoplasm.
What does the Central Dogma describe?
DNA → mRNA → Protein
They determine folding through interactions like hydrophobic/hydrophilic forces and ionic bonds.
How do R groups affect protein folding?
Brings amino acids to the ribosome and matches them with codons via its anticodon.
What is the function of tRNA?
What are the four main levels of gene regulation?
Transcriptional, post-transcriptional, translational, and post-translational.
Why don’t antibiotics kill human cells?
Antibiotics target bacterial ribosomes, which differ from eukaryotic ribosomes.
What causes lactose tolerance in humans?
A regulatory mutation keeps lactase gene expression active in adults.
Peptide bond (formed by dehydration synthesis).
What type of bond joins amino acids together?
Where does translation occur in eukaryotic cells?
In the cytoplasm, on ribosomes.
How does RNA interference (RNAi) regulate genes?
Small RNAs bind to mRNA and prevent it from being translated.
Why do bacterial genes form operons?
To group related genes together for efficient regulation and expression only when needed.
Give one example of gene regulation in evolution.
Mutations in promoters or enhancers can alter when genes are expressed, affecting traits.
Name and describe the four levels of protein structure.
Primary: amino acid sequence; Secondary: α-helix & β-sheet; Tertiary: 3D folding; Quaternary: multiple polypeptides together.
What is the start codon, and which amino acid does it code for?
AUG — methionine
In Texel sheep, how does RNA stability affect muscle phenotype?
Mutation creates a site for microRNA binding, reducing mRNA for a muscle inhibitor — resulting in double muscling.
Compare inducible and repressible operons.
Inducible (lac) = turned on by substrate; Repressible (trp) = turned off by product.
Why do cells not express all genes all the time?
To save energy and resources — only express genes needed for current conditions.
Misfolded proteins cause other proteins to misfold, leading to diseases like mad cow or Creutzfeldt–Jakob.
What happens when proteins misfold, as in prion diseases?
Briefly describe the three stages of translation.
Initiation (ribosome assembles), elongation (amino acids added), termination (stop codon signals release).
How does gene regulation at the transcription level affect stickleback fish phenotype?
Deletion in a transcriptional enhancer removes pelvic spine development gene expression.
Compare the Central Dogma in prokaryotes vs. eukaryotes.
Prokaryotes: transcription and translation occur together; Eukaryotes: separated, with RNA processing in the nucleus.
How might errors in gene regulation cause disease?
Faulty splicing, promoter mutations, or misfolded proteins can lead to cancer or genetic disorders.