Cycle 2 Flashcards
Q: What is a gene?
A: A DNA sequence that is transcribed into RNA.
Q: Name the three major classes of genes and their proportions in the total RNA pool.
mRNA (5%): Carries instructions to make protein.
tRNA (10%): Functional as RNA molecules.
rRNA (85%): Functional as RNA, highly abundant due to ribosome production.
Q: What is the role of the promoter in a gene?
A: The promoter regulates whether a gene is turned on or off. It is a piece of DNA that is not transcribed.
Q: What is the transcription unit?
A: The part of the gene that gets transcribed into RNA.
Q: Why is RNA thought to have evolved before DNA and proteins?
A: RNA carries information like DNA and can acquire 3D shapes and catalytic properties like proteins (ribozymes).
Q: Describe the central dogma of molecular biology.
A: DNA → RNA → Protein. Information flows from DNA to RNA through transcription, and from RNA to protein through translation.
Q: What are the three types of gene expression?
Constitutive: Always active.
Induced: Activated under specific conditions.
Repressed: Activity is decreased.
Q: What is the role of tRNA and rRNA compared to mRNA?
tRNA and rRNA: Functional as RNA molecules, directly involved in protein synthesis.
mRNA: Carries genetic information to make proteins.
Q: Why does RNA degrade more easily than DNA?
A: RNA has an OH group in its sugar backbone, making it more unstable and prone to enzymatic degradation by ribonucleases.
Q: Why is it beneficial for mRNA to degrade quickly?
A: To prevent the accumulation of faulty or unnecessary transcripts, ensuring precise temporal regulation of gene expression.
Q: What is the function of heat shock proteins (HSPs)?
A: HSPs act as molecular chaperones, helping other proteins remain functional at high temperatures.
Q: How do you check if RNA is degraded in the lab?
A: Run the sample on a gel; degraded RNA will show no white bands.
Q: What are “omics,” and what do they study?
Omics characterizes groups of molecules:
Genomics: DNA.
Transcriptomics: mRNA.
Proteomics: Proteins.
Metabolomics: Metabolic products.
Q: Why are proteomics and metabolomics more informative than genomics and transcriptomics?
A: They reveal functional differences by analyzing protein profiles and metabolic activities.
Q: What was observed in the Chlamydomonas heat shock experiment?
Hsp1 Transcript: Increased during extreme heat (induced).
Actin Protein: Constant levels (constitutive expression).
HSP1 Protein: Increased with time, correlating with transcript levels.
Q: What is the difference between transcript abundance and protein abundance?
Transcript abundance: Depends on transcription rates and mRNA decay.
Protein abundance: Depends on translation rates and protein degradation.
Q1: What is the TB12 phenotype in mice?
A: Complete blindness.
Q2: Why is retinal not considered a gene product?
A: Retinal is a pigment produced via a biosynthetic pathway, not a protein coded by genes.
Q3: What is the relationship between retinal and opsin?
A: Retinal (a cofactor) binds to opsin (apoprotein) post-translation to form a functional complex.
Q4: Define apoprotein.
A: A protein without its cofactor.
Q5: What are cofactors, and give an example?
A: Molecules that bind to proteins to enable their function; example: copper.
Q6: What is forward genetics?
A: Linking phenotype to genotype to identify the gene(s) responsible for a phenotype.
Q7: What is reverse genetics?
A: Using genotype to phenotype by knocking out a gene to determine its function.
Q8: What are the steps of forward genetics?
Generate a mutagenized population of cells.
Screen the mutant population for a phenotype.
Identify the mutated gene.
Prove the mutated gene causes the phenotype (genetic complementation).
