Podcast
Questions and Answers
What modification is applied to the 5' end of eukaryotic mRNA during processing?
What modification is applied to the 5' end of eukaryotic mRNA during processing?
Which of the following sequences are retained in the functional mRNA after processing?
Which of the following sequences are retained in the functional mRNA after processing?
What is the role of the spliceosome in RNA splicing?
What is the role of the spliceosome in RNA splicing?
Which feature of the poly-A tail is NOT associated with eukaryotic mRNA?
Which feature of the poly-A tail is NOT associated with eukaryotic mRNA?
Signup and view all the answers
What is the relationship between introns and exons in eukaryotic genes?
What is the relationship between introns and exons in eukaryotic genes?
Signup and view all the answers
During RNA splicing, what shape does the excised intron take?
During RNA splicing, what shape does the excised intron take?
Signup and view all the answers
What do codons in mRNA represent during translation?
What do codons in mRNA represent during translation?
Signup and view all the answers
What is the function of the snRNPs in RNA splicing?
What is the function of the snRNPs in RNA splicing?
Signup and view all the answers
What did Archibald Garrod propose in 1909 regarding genes and phenotypes?
What did Archibald Garrod propose in 1909 regarding genes and phenotypes?
Signup and view all the answers
What does the term 'auxotrophs' refer to?
What does the term 'auxotrophs' refer to?
Signup and view all the answers
Which hypothesis was established based on Beadle and Tatum's experiments?
Which hypothesis was established based on Beadle and Tatum's experiments?
Signup and view all the answers
What is the first step in the process of going from DNA to protein?
What is the first step in the process of going from DNA to protein?
Signup and view all the answers
What role does the anticodon portion of tRNA play?
What role does the anticodon portion of tRNA play?
Signup and view all the answers
What is the main structural difference between DNA and RNA?
What is the main structural difference between DNA and RNA?
Signup and view all the answers
Which of the following statements about aminoacyl-tRNA synthetases is correct?
Which of the following statements about aminoacyl-tRNA synthetases is correct?
Signup and view all the answers
Why was the one gene-one enzyme hypothesis modified to the one gene-one polypeptide hypothesis?
Why was the one gene-one enzyme hypothesis modified to the one gene-one polypeptide hypothesis?
Signup and view all the answers
What is the primary function of RNA polymerase during transcription?
What is the primary function of RNA polymerase during transcription?
Signup and view all the answers
Which of the following components of the ribosome is primarily made up of rRNA?
Which of the following components of the ribosome is primarily made up of rRNA?
Signup and view all the answers
What role do transcription factors play in eukaryotic transcription?
What role do transcription factors play in eukaryotic transcription?
Signup and view all the answers
What is the process called that converts RNA to protein?
What is the process called that converts RNA to protein?
Signup and view all the answers
In which cellular compartment does transcription occur in eukaryotes?
In which cellular compartment does transcription occur in eukaryotes?
Signup and view all the answers
What happens at the P site of the ribosome?
What happens at the P site of the ribosome?
Signup and view all the answers
What characteristic is not true regarding wild-type yeast?
What characteristic is not true regarding wild-type yeast?
Signup and view all the answers
What structure in the DNA is recognized by RNA polymerase prior to initiating transcription?
What structure in the DNA is recognized by RNA polymerase prior to initiating transcription?
Signup and view all the answers
Why is a triplet of nucleotides necessary for coding amino acids?
Why is a triplet of nucleotides necessary for coding amino acids?
Signup and view all the answers
What happens during the elongation phase of transcription?
What happens during the elongation phase of transcription?
Signup and view all the answers
What does it mean that the genetic code has redundancy?
What does it mean that the genetic code has redundancy?
Signup and view all the answers
Which of the following correctly describes the relationship between codons and amino acids?
Which of the following correctly describes the relationship between codons and amino acids?
Signup and view all the answers
What are the components of a transcription unit?
What are the components of a transcription unit?
Signup and view all the answers
How does transcription differ between prokaryotes and eukaryotes?
How does transcription differ between prokaryotes and eukaryotes?
Signup and view all the answers
How many triplet codons do not code for any amino acids?
How many triplet codons do not code for any amino acids?
Signup and view all the answers
What is the role of the terminator in transcription?
What is the role of the terminator in transcription?
Signup and view all the answers
What is the primary role of the reading frame in translation?
What is the primary role of the reading frame in translation?
Signup and view all the answers
What phenomenon allows for the utilization of only 45 different tRNAs for 64 codons?
What phenomenon allows for the utilization of only 45 different tRNAs for 64 codons?
Signup and view all the answers
During the elongation cycle of translation, which factor is required for energy provision?
During the elongation cycle of translation, which factor is required for energy provision?
Signup and view all the answers
Which of the following correctly describes the process of translocation during translation?
Which of the following correctly describes the process of translocation during translation?
Signup and view all the answers
What is the function of the release factor during translation termination?
What is the function of the release factor during translation termination?
Signup and view all the answers
How do signal peptides function in protein targeting?
How do signal peptides function in protein targeting?
Signup and view all the answers
What is the significance of polyribosomes in protein synthesis?
What is the significance of polyribosomes in protein synthesis?
Signup and view all the answers
Which codons are recognized as stop codons in the translation process?
Which codons are recognized as stop codons in the translation process?
Signup and view all the answers
Study Notes
DNA to Protein
- DNA provides instructions, proteins are the results
- Molecular Genetics: study of metabolic defects demonstrates genes lead to proteins
- Archibald Garrod (1909): first proposed this relationship
- Genes dictate phenotypes via enzymes; inherited diseases caused by enzyme lack
- Beadle and Tatum (1930s): confirmed gene control of metabolism via experiments with yeast (Neurospora crassa) and X-ray-generated mutants.
Gene Control of Metabolism
- Mutations in yeast blocked various steps in arginine synthesis pathway (Fig 17.2)
- Wild-type yeast survived on minimal medium
- Mutants required specific nutrients (auxotrophs)
One Gene-One Enzyme Hypothesis
- Modified to one gene-one polypeptide hypothesis
- Not all proteins are enzymes
- Many enzymes are 2 polypeptide subunits
Steps from DNA to Protein
- DNA → RNA → Proteins
- Transcription: DNA to RNA
- RNA is complementary to DNA
- mRNA for proteins
DNA verses RNA
- Both are polymers of nucleotides
- DNA: deoxyribose sugar, thymine base
- RNA: ribose sugar, uracil base
RNA to Protein (Translation)
- Process of RNA to protein is called translation
- mRNA synthesized from a gene dictates protein sequence
Steps in Transcription
- RNA polymerase separates DNA helix at initiation sequence
- Enzymatically builds RNA chain complementary to DNA template strand
- Stops at terminator sequence
Transcription Unit
- Initiation site + gene + terminator
Promoter Region
- In eukaryotes, RNA polymerase needs transcription factors to recognize promoter region
- Specific transcription factor binds to the TATA box region
- RNA polymerase binds and separates the DNA strands at initiation site
Elongation of RNA Strand
- RNA polymerase unwinds DNA double helix
- Catalyzes addition of RNA nucleotides to 3’ end of RNA molecule
Termination of Transcription
- Terminator sequence in DNA signals end of transcription unit
- Termination factors may interact with DNA
Eukaryotic RNA Modifications
- RNA processing before export from nucleus:
- Addition of 5' cap
- Addition of poly-A tail to 3' end
- Removal of introns (non-coding regions) and splicing of exons (coding regions) to form mature mRNA.
RNA Splicing
- Eukaryotic genes have introns (non-coding) and exons (coding regions)
- Splicing removes the introns
- Small nuclear ribonucleoproteins (snRNPs) and spliceosome facilitate splicing
- Resulting mRNA contains mature exon sequences
Domains
- Domains are distinct portions of a protein coded for by exons
- Exons can swap between proteins
Translation
- RNA directed synthesis of polypeptides
- tRNA acts as an interpreter
- Anticodon on tRNA complements the codon on mRNA specifying an amino acid
- Aminoacyl-tRNA synthetases attach amino acids to specific tRNA molecules
Ribosomes
- Ribosomes synthesize proteins
- Sites for polypeptide assembly and tRNA anticodon-mRNA codon interactions
- Composed of ribosomal RNA (rRNA) and protein subunits
- Includes 3 binding sites; A(aminoacyl-tRNA), P(peptidyl-tRNA), and E (exit) sites
Elongation Cycle of Translation (Fig 17.20)
- tRNA anticodon binds to mRNA codon
- Peptide bond formation
- Translocation to next amino acid
- Energy for steps is provided by GTP
Termination of Translation
- mRNA reaches stop codon
- Release factor binds to A site
- Polypeptide chain is released from tRNA
Polyribosomes
- Multiple ribosomes translate a single mRNA molecule -> many protein copies quickly
Protein Targeting
- Signal peptides direct proteins to specific locations
- Signal recognition particle (SRP) guides protein to proper cellular compartment
Coupled Transcription-Translation (Prokaryotes)
- Prokaryotic mRNA translated as soon as transcribed
- No mRNA processing required before translation starts
Mutations
- Point mutations (substitutions, missense, nonsense, insertions, deletions, frameshifts )
- Mutagens cause mutations
- Mutations can have varied severity (or no observable effects)
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
