Podcast
Questions and Answers
What is the role of the branch site during intron splicing?
What is the role of the branch site during intron splicing?
- To facilitate the formation of a lariat structure (correct)
- To cleave the 5’ end of the intron
- To enhance stability of the mRNA
- To serve as a donor site for the intron
Which component is part of the spliceosome responsible for intron removal?
Which component is part of the spliceosome responsible for intron removal?
- Protein-encoding genes
- Eukaryotic ribosomes
- mRNA
- Small nuclear RNAs (snRNAs) (correct)
How does the addition of a poly(A) tail contribute to mRNA functionality?
How does the addition of a poly(A) tail contribute to mRNA functionality?
- Increases mRNA stability and aids in nuclear export (correct)
- Provides recognition sites for spliceosome binding
- Facilitates the initiation of transcription
- Contributes to the degradation of mRNA
Which sequence element marks the initiation site of transcription?
Which sequence element marks the initiation site of transcription?
What is the main purpose of the splice donor and acceptor sites?
What is the main purpose of the splice donor and acceptor sites?
Which of the following best describes the role of the spliceosome?
Which of the following best describes the role of the spliceosome?
During mRNA transcription, which sequence represents the transcribed RNA from the DNA sequence 5’–GATTCGAAGCT–3’?
During mRNA transcription, which sequence represents the transcribed RNA from the DNA sequence 5’–GATTCGAAGCT–3’?
What is one key difference between RNA and DNA?
What is one key difference between RNA and DNA?
What happens during step 2 of the intron splicing process?
What happens during step 2 of the intron splicing process?
Which type of RNA is most abundant in eukaryotic cells?
Which type of RNA is most abundant in eukaryotic cells?
What is the primary function of transfer RNA (tRNA)?
What is the primary function of transfer RNA (tRNA)?
What percentage of total RNA does messenger RNA (mRNA) typically represent?
What percentage of total RNA does messenger RNA (mRNA) typically represent?
What sequence length characterizes microRNA (miRNA)?
What sequence length characterizes microRNA (miRNA)?
Which of the following statements about ribosomal RNA (rRNA) is accurate?
Which of the following statements about ribosomal RNA (rRNA) is accurate?
Which type of RNA is involved in regulating gene expression?
Which type of RNA is involved in regulating gene expression?
What is the role of the anticodon found in tRNA?
What is the role of the anticodon found in tRNA?
Which statement about the genetic code is true?
Which statement about the genetic code is true?
What is the first step in the process of translational initiation?
What is the first step in the process of translational initiation?
Where is ribosomal RNA (rRNA) synthesized in eukaryotic cells?
Where is ribosomal RNA (rRNA) synthesized in eukaryotic cells?
Which factors affect the regulation of translational initiation?
Which factors affect the regulation of translational initiation?
During the elongation phase of translation, what is formed by the action of peptidyl-transferase?
During the elongation phase of translation, what is formed by the action of peptidyl-transferase?
In which direction is mRNA translated during protein synthesis?
In which direction is mRNA translated during protein synthesis?
What happens when the ribosome encounters a termination codon?
What happens when the ribosome encounters a termination codon?
Which of the following is a role of eukaryotic initiation factors (eIFs)?
Which of the following is a role of eukaryotic initiation factors (eIFs)?
What is the role of the methylguanosine cap binding complex (CBC) in translational initiation?
What is the role of the methylguanosine cap binding complex (CBC) in translational initiation?
What is the primary function of the eukaryotic release factor (eRF)?
What is the primary function of the eukaryotic release factor (eRF)?
Which sequence element defines the 5’ end of an intron?
Which sequence element defines the 5’ end of an intron?
What role does histone acetylation play in transcription?
What role does histone acetylation play in transcription?
Which sequence element determines the site of transcription initiation?
Which sequence element determines the site of transcription initiation?
What is the genetic code primarily responsible for?
What is the genetic code primarily responsible for?
How many different codons are possible with the four nucleotides in mRNA?
How many different codons are possible with the four nucleotides in mRNA?
What characterizes the genetic code as 'degenerate'?
What characterizes the genetic code as 'degenerate'?
Which of the following codons serves as a termination signal?
Which of the following codons serves as a termination signal?
How is the directionality of mRNA sequence described?
How is the directionality of mRNA sequence described?
What is the cause of Tay-Sachs disease?
What is the cause of Tay-Sachs disease?
Which disease is characterized by the accumulation of all acid hydrolases due to defective phosphorylation of mannose?
Which disease is characterized by the accumulation of all acid hydrolases due to defective phosphorylation of mannose?
What distinguishes regulated secretion from constitutive secretion?
What distinguishes regulated secretion from constitutive secretion?
Which of the following options is a common feature of lysosomal storage diseases?
Which of the following options is a common feature of lysosomal storage diseases?
What is the typical lifespan of a child with the infantile form of Tay-Sachs disease?
What is the typical lifespan of a child with the infantile form of Tay-Sachs disease?
What is a characteristic clinical feature of Tay-Sachs disease?
What is a characteristic clinical feature of Tay-Sachs disease?
What type of secretion involves vesicles that bud off and continuously release contents outside the cell?
What type of secretion involves vesicles that bud off and continuously release contents outside the cell?
Which condition results from mutations in the HEXA gene?
Which condition results from mutations in the HEXA gene?
Flashcards
Transcription
Transcription
Process of copying genetic information from DNA to RNA.
RNA vs. DNA
RNA vs. DNA
RNA sugar is ribose, uracil replaces thymine, and it's single-stranded.
Types of RNA
Types of RNA
rRNA, tRNA, mRNA, and miRNA.
Ribosomal RNA (rRNA)
Ribosomal RNA (rRNA)
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Transfer RNA (tRNA)
Transfer RNA (tRNA)
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Messenger RNA (mRNA)
Messenger RNA (mRNA)
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MicroRNA (miRNA)
MicroRNA (miRNA)
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Splicing of Introns
Splicing of Introns
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Spliceosome
Spliceosome
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Splice donor/acceptor sites
Splice donor/acceptor sites
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Branch Site (Adenosine)
Branch Site (Adenosine)
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Nuclear Pores
Nuclear Pores
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Poly(A) Tail Addition
Poly(A) Tail Addition
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Histone Acetylation
Histone Acetylation
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Genetic Code
Genetic Code
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Codon
Codon
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61/64 Codons
61/64 Codons
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Stop Codons
Stop Codons
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Specific (Codons)
Specific (Codons)
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Universal (genetic code)
Universal (genetic code)
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Degenerate/Redundant (Codons)
Degenerate/Redundant (Codons)
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Translation initiation
Translation initiation
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Regulation of Translational Initiation
Regulation of Translational Initiation
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eIFs
eIFs
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Elongation (Translation)
Elongation (Translation)
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Termination (Translation)
Termination (Translation)
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STOP codons
STOP codons
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Lysosomal Storage Diseases
Lysosomal Storage Diseases
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I-Cell Disease (GNPTAB mutations)
I-Cell Disease (GNPTAB mutations)
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Secreted Proteins
Secreted Proteins
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Study Notes
Transcription
- Transcription: the process of copying genetic information from DNA to RNA
- Difference between DNA and RNA: the sugar in RNA is ribose, unlike deoxyribose in DNA, RNA has uracil instead of thymine, RNA is single stranded
- Types of RNA: ribosomal RNA (rRNA), transfer RNA (tRNA), messenger RNA (mRNA), microRNA (miRNA)
- Ribosomal rRNA: accounts for ~80% of total RNA, synthesized in the nucleolus, exists in multiple copies in the genome, 4 eukaryotic rRNAs: 28S, 18S, 5.8S and 5S, associate with proteins to form ribosomes, essential for protein synthesis
- Transfer tRNA: accounts for ~15% of total RNA, synthesized in the nucleus, carries specific amino acids, at least one tRNA per amino acid, required for protein synthesis
- Messenger mRNA: accounts for ~5% of total RNA, synthesized in the nucleus, carries genetic information from DNA to the cytosol, also referred to as transcripts, heterogeneous in size and sequence
- MicroRNA miRNA: ~22 nucleotides in length, bind to 3’UTR of specific mRNAs, regulate gene expression by repressing protein production or triggering mRNA degradation
- Splicing of introns: three-step process leading to removal of introns, requires spliceosome assembly
- Spliceosome: composed of pre-mRNA, five small nuclear RNAs and proteins (snRNPs), ~50 proteins
- Splice donor and acceptor sites: define the beginning and end of an intron
- Branch site: contains an Adenosine (A) with an -OH group
- Step 1: spliceosome recognizes donor and acceptor sites, brings the ends of the intron together
- Step 2: hydroxyl group on the branch site A attacks the donor site, cleavage of intron at 5’ end, formation of a phosphodiester bond and lariat-like structure
- Step 3: the cleaved 3’ end of exon 1 attacks the 5’ end of exon 2, intron is removed, exon ends are joined by a phosphodiester bond, spliceosome disassembles, mature mRNA is formed
- Nuclear pores: function in exporting mature mRNA from the nucleus
- Prokaryotes: continuous, fast transcription
- Eukaryotes: transcription is more complex
- Poly (A) tail addition: essential for stability and nuclear export, protects the mRNA from endonuclease activity
- 5' end of an intron: defined by a splice donor site
- Histone acetylation: required for activation of transcription
Translation
- Genetic code: set of rules used by ribosomes to translate DNA/RNA information into proteins, a link between nucleotide sequence and amino acid sequence
- Codon: a sequence of three nucleotides that specifies a given amino acid
- Codons: written and read in 5’-to-3’ direction, 64 different codons
- 61/64 codons: encode the 20 amino acids
- 3/64 codons: are termination signals, UAG, UGA, UAA
- Specific: a codon always codes for the same amino acid
- Universal: conserved across species, very few variations in mitochondrial code, specific yeast and bacteria types
- Degenerate (or redundant): an amino acid can be specified by more than one codon
- Initiation: assembly of ribosomal subunits, initiator aminoacyl-tRNA, eukaryotic initiation factors (eIFs), and mRNA
- Regulation of Translational Initiation: rate-limiting step involves binding of the 5’ m7Gp Cap by the methylguanosine cap binding complex (CBC)
- eIFs: control points for regulating initiation, globin synthesis in reticulocytes is regulated by heme availability
- Elongation: ribosome moves along the mRNA in a multistep process, involves binding of incoming aminoacyl-tRNA to the A site, peptide bond formation, translocation of the ribosome alongside mRNA
- Termination: ribosome reaches a termination codon, binding of eukaryotic release factor (eRF) to the A site, release of polypeptide chain from ribosome, dissociation of the ribosome-mRNA complex + recycling of components
- STOP CODONS: UAA, UAG, UGA
Protein Trafficking
- Lysosomal storage diseases: accumulation of undegraded substances due to defective lysosomal enzymes
- I cell disease (GNPTAB mutations): impaired targeting of all acid hydrolases to lysosomes due to defective phosphorylation of mannose
- Hurler & Hunter syndromes (IDUA or IDS mutations): Mucopolysaccharidosis types I & II
- Tay-Sachs disease (HEXA mutations): accumulation of glycolipids (GM2 gangliosides) in the brain due to a lack of the hydrolytic enzyme in lysosomes, progressive deterioration of nerve cells, death by age 4 (infantile form), characteristic "Cherry Red Spot" in the retina, over 120 different mutations, single nucleotide insertions/deletions, splice site mutations, missense mutations
- Secreted proteins: reach the Golgi, lack a retention signal for the Golgi, lysosomes, or plasma membrane, secreted outside the cell, encapsulated in transport vesicles, bud off from the Trans-Golgi Network, two options: constitutive secretion and regulated secretion
- Constitutive secretion: fuses with the plasma membrane and is secreted continuously, transports large molecules from cells
- Regulated secretion: stored in the cytoplasm and only secreted at specific times, a discontinuous process, occurs in response to signals
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Description
This quiz explores the transcription process, detailing the key differences between DNA and RNA. It covers the various types of RNA, including their functions, synthesis, and significance in protein synthesis. Test your understanding of ribosomal RNA, transfer RNA, messenger RNA, and microRNA.
