Gene Expression and Central Dogma
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Questions and Answers

What is the first step in the gene expression process?

  • Transcription (correct)
  • Translation
  • Gene editing
  • Post-translational modification

    • Which role does tRNA play in protein synthesis?

  • They catalyze the formation of nucleotides
  • They act as a template for DNA replication
  • They bring amino acids to the ribosome (correct)
  • They synthesize the RNA

    • What is the role of ribosomes during protein synthesis?

  • To initiate DNA replication
  • To provide energy for protein folding
  • To match tRNA anticodons with mRNA codons (correct)
  • To modify RNA after transcription

    • Which of the following is involved in the post-translation modification of proteins?

    <p>Proteases</p> Signup and view all the answers

    What can result from mutations in the coding sequence of RNA?

    <p>Changes in the amino acid sequence</p> Signup and view all the answers

    Which best describes the concept of 'inborn errors of metabolism' as proposed by Archibald Garrod?

    <p>Inherited diseases that are caused by enzyme deficiencies</p> Signup and view all the answers

    What is the primary function of CRISPR-Cas9 technology?

    <p>To edit specific genes</p> Signup and view all the answers

    What mechanism is involved in making tRNAs 'charged' with amino acids?

    <p>Aminoacyl-tRNA synthetase activity</p> Signup and view all the answers

    What type of mutation is characterized by a change in a nucleotide pair that results in an early stop codon?

    <p>Nonsense mutation</p> Signup and view all the answers

    Which type of mutation is likely to have the most severe effect on protein function?

    <p>Insertion mutation</p> Signup and view all the answers

    How do mutations occur during DNA replication?

    <p>Through nucleotide-pair substitutions, insertions, or deletions</p> Signup and view all the answers

    What is the role of mutagens in mutation development?

    <p>They cause specific or random changes in DNA</p> Signup and view all the answers

    Which type of mutation does NOT generally affect protein function?

    <p>Silent mutation</p> Signup and view all the answers

    What is the primary consequence of a frameshift mutation?

    <p>Alteration in the grouping of codons</p> Signup and view all the answers

    What type of mutations are more likely to be spontaneous?

    <p>Nucleotide-pair substitutions</p> Signup and view all the answers

    How do bacteria primarily regulate gene expression?

    <p>By adjusting transcription levels</p> Signup and view all the answers

    What effect does feedback inhibition have in metabolic pathways?

    <p>Inhibits the final product's synthesis</p> Signup and view all the answers

    What is one role of noncoding RNAs in gene expression regulation?

    <p>They modify chromatin structure</p> Signup and view all the answers

    In which environment would a bacterium likely stop producing tryptophan?

    <p>In a tryptophan-rich environment</p> Signup and view all the answers

    What is typically the result of a missense mutation?

    <p>Change of one amino acid for another</p> Signup and view all the answers

    Which mutation typically occurs due to errors during DNA replication?

    <p>Substitutions between nucleotide pairs</p> Signup and view all the answers

    What role does rRNA play in ribosomal function?

    <p>Catalyzes the formation of peptide bonds</p> Signup and view all the answers

    Which site in the ribosome is responsible for holding the tRNA that carries the growing polypeptide chain?

    <p>P site</p> Signup and view all the answers

    What is the primary energy source used during the elongation stage of translation?

    <p>GTP</p> Signup and view all the answers

    What triggers the termination of translation?

    <p>The arrival of a stop codon at the A site</p> Signup and view all the answers

    Which phase of translation involves the assembly of the initiation complex?

    <p>Initiation</p> Signup and view all the answers

    How does the ribosome ensure the accuracy of codon recognition during translation?

    <p>By hydrolizing GTP</p> Signup and view all the answers

    What is the fate of the tRNA once it has released its amino acid?

    <p>It leaves the ribosome at the E site</p> Signup and view all the answers

    What is the primary structural contributor to the ribosome's function?

    <p>rRNA</p> Signup and view all the answers

    What type of mutation directly affects only a single nucleotide pair?

    <p>Point mutation</p> Signup and view all the answers

    What is the role of the mRNA in protein synthesis?

    <p>To convey genetic information from DNA to ribosomes</p> Signup and view all the answers

    During translation, how is the polypeptide carried from the ribosome to the cytosol?

    <p>Through the exit tunnel of the large subunit</p> Signup and view all the answers

    Which factors help in the assembly of the translation initiation complex?

    <p>Initiation factors</p> Signup and view all the answers

    Which of the following statements about codons is correct?

    <p>Codons are triplets of nucleotides that specify amino acids</p> Signup and view all the answers

    What is the primary function of chaperone proteins during protein synthesis?

    <p>Aid in polypeptide folding</p> Signup and view all the answers

    What is the significance of the AUG codon during translation?

    <p>It codes for the amino acid methionine and signifies the start of translation</p> Signup and view all the answers

    What is the primary function of RNA polymerase in transcription?

    <p>To synthesize mRNA from the DNA template</p> Signup and view all the answers

    Polyribosomes are structures formed by?

    <p>Multiple ribosomes translating the same mRNA</p> Signup and view all the answers

    How does RNA polymerase differ from DNA polymerase during nucleotide assembly?

    <p>RNA polymerase does not need a primer to begin synthesis</p> Signup and view all the answers

    The region of the DNA where RNA polymerase binds to initiate transcription is known as the:

    <p>Promoter</p> Signup and view all the answers

    How many codons are there that specify amino acids?

    <p>61</p> Signup and view all the answers

    Why is it essential to establish the correct reading frame during transcription?

    <p>To decode the mRNA correctly into amino acids</p> Signup and view all the answers

    What does the presence of a TATA box indicate in transcription?

    <p>It is crucial for RNA polymerase binding during initiation</p> Signup and view all the answers

    What ensures that the genetic code has redundancy without ambiguity?

    <p>Several codons can code for the same amino acid</p> Signup and view all the answers

    What does the term 'nonoverlapping' refer to in the context of codons?

    <p>Codons are read independently without sharing nucleotides</p> Signup and view all the answers

    What is the significance of the terminator in transcription?

    <p>It indicates the end of the transcription process</p> Signup and view all the answers

    In eukaryotes, how are transcription factors involved in transcription initiation?

    <p>They facilitate the binding of RNA polymerase to the promoter</p> Signup and view all the answers

    What is the directionality of mRNA synthesis during transcription?

    <p>5′ to 3′</p> Signup and view all the answers

    What is the main conclusion drawn by Beadle and Tatum from their experiments with Neurospora crassa?

    <p>Each mutant defect is linked to a specific gene responsible for enzyme production.</p> Signup and view all the answers

    How did Srb and Horowitz contribute to understanding the synthesis of arginine in mutants?

    <p>They categorically linked each mutant to specific deficiencies in distinct enzymes.</p> Signup and view all the answers

    What does the one gene-one polypeptide hypothesis acknowledge that the one gene-one enzyme hypothesis did not?

    <p>Genes may code for several polypeptides not identified as enzymes.</p> Signup and view all the answers

    What is the primary role of messenger RNA (mRNA) in protein synthesis?

    <p>To carry the genetic instructions from DNA to ribosomes.</p> Signup and view all the answers

    Which of the following statements is true regarding the structure of RNA?

    <p>RNA usually consists of a single strand.</p> Signup and view all the answers

    What is the term for the initial RNA transcript before processing in eukaryotic cells?

    <p>Pre-mRNA</p> Signup and view all the answers

    What is the concept called that describes the flow of genetic information from DNA to RNA to protein?

    <p>The central dogma</p> Signup and view all the answers

    Why is the genetic code considered to be triplet-based?

    <p>Each amino acid is specified by a triplet of nucleotide bases.</p> Signup and view all the answers

    How does transcription in eukaryotic cells differ from transcription in bacteria?

    <p>Transcription occurs in the nucleus in eukaryotes.</p> Signup and view all the answers

    Which statement accurately describes ribosomes' function in translation?

    <p>Ribosomes facilitate the assembly of amino acids into polypeptide chains.</p> Signup and view all the answers

    What is indicated by alternative splicing in eukaryotic genes?

    <p>Different polypeptides can be produced from the same gene.</p> Signup and view all the answers

    Which of the following is NOT a role of RNA in the cell?

    <p>Providing a template for DNA replication.</p> Signup and view all the answers

    What ultimately determines the primary structure of proteins?

    <p>The ordered sequence of amino acids specified by mRNA.</p> Signup and view all the answers

    What discovery supported the one gene-one enzyme hypothesis?

    <p>The relationship between mutant strains and enzyme deficiencies.</p> Signup and view all the answers

    What is the primary level at which cells regulate gene expression for enzyme production?

    <p>Transcription</p> Signup and view all the answers

    What is the role of RNA splicing in mRNA processing?

    <p>To remove introns and join exons</p> Signup and view all the answers

    What is the role of the operator in the operon model?

    <p>To control the access of RNA polymerase to the genes</p> Signup and view all the answers

    Which protein in the trp operon is responsible for turning off the expression of the operon?

    <p>trp repressor</p> Signup and view all the answers

    Which of the following correctly describes a primary function of the 5' cap and poly-A tail on mRNA?

    <p>To facilitate mRNA export from the nucleus and protect it</p> Signup and view all the answers

    What is an anticodon?

    <p>A three-nucleotide sequence on tRNA that pairs with mRNA codons</p> Signup and view all the answers

    Why is the trp operon not permanently switched off?

    <p>Repressor binding to the operator is reversible</p> Signup and view all the answers

    What function does tryptophan serve in the trp operon?

    <p>It acts as a corepressor</p> Signup and view all the answers

    What is the function of aminoacyl-tRNA synthetase?

    <p>To attach amino acids to the correct tRNA</p> Signup and view all the answers

    What is the purpose of the spliceosome during RNA processing?

    <p>To remove introns and join exons in premRNA</p> Signup and view all the answers

    What type of operon is the trp operon classified as?

    <p>Repressible operon</p> Signup and view all the answers

    Which of the following correctly describes the operation of the lac operon?

    <p>Lactose presence inactivates the repressor.</p> Signup and view all the answers

    Which statement about tRNA is accurate?

    <p>Each tRNA carries a specific amino acid to ribosomes</p> Signup and view all the answers

    What happens when lactose is absent in the environment of E. coli?

    <p>Most of the lac repressor is active.</p> Signup and view all the answers

    What characterizes the wobble phenomenon in tRNA?

    <p>Relaxed base pairing rules for the third base of codons</p> Signup and view all the answers

    Which of the following components is NOT part of the ribosome?

    <p>snRNA</p> Signup and view all the answers

    How does the presence of tryptophan affect the activity of the trp repressor?

    <p>It activates the repressor by binding to its allosteric site.</p> Signup and view all the answers

    What type of regions are UTRs in mRNA?

    <p>Non-coding regions that remain untranslated</p> Signup and view all the answers

    What is the primary difference between repressible and inducible operons?

    <p>Repressible operons are inhibited by small molecules, while inducible operons are stimulated by them.</p> Signup and view all the answers

    How do ribosomes facilitate translation?

    <p>By correctly matching tRNA anticodons with mRNA codons</p> Signup and view all the answers

    How many genes coding for the subunits of enzymes involved in tryptophan synthesis are clustered in the trp operon?

    <p>Five</p> Signup and view all the answers

    The sequence of events during translation begins with the binding of which molecule to the ribosome?

    <p>mRNA molecule</p> Signup and view all the answers

    What is the function of ß-galactosidase in the lac operon?

    <p>It hydrolyzes lactose into glucose and galactose.</p> Signup and view all the answers

    What is the average length of a transcription unit in human DNA?

    <p>About 27,000 nucleotide pairs</p> Signup and view all the answers

    What occurs when tryptophan concentration in E. coli cells is low?

    <p>Transcription of the operon resumes.</p> Signup and view all the answers

    Which component of the lac operon operates as an allosteric repressor?

    <p>lacI protein</p> Signup and view all the answers

    What happens to the introns in mRNA processing?

    <p>They are removed during splicing</p> Signup and view all the answers

    What is a primary characteristic of small nuclear ribonucleoproteins (snRNPs)?

    <p>They function in splicing RNA molecules</p> Signup and view all the answers

    How are ribosomal subunits produced in eukaryotes?

    <p>In the nucleolus from rRNA transcribed and assembled with proteins</p> Signup and view all the answers

    What is the primary function of allolactose in gene expression?

    <p>To induce enzyme synthesis by freeing the lac operon from the repressor</p> Signup and view all the answers

    What characterizes differential gene expression in multicellular eukaryotes?

    <p>Only a small percentage of genes are expressed at any time</p> Signup and view all the answers

    What effect does histone acetylation have on gene transcription?

    <p>It relaxes chromatin structure, facilitating access for transcription</p> Signup and view all the answers

    In what way do methylation and histone modification potentially interact?

    <p>Histone modifications can recruit methylation enzymes to specific genes</p> Signup and view all the answers

    What role does chromatin structure play in gene expression?

    <p>The organization of chromatin directly influences transcriptional activity</p> Signup and view all the answers

    What is the effect of DNA methylation on gene expression?

    <p>It reduces gene expression in most cases</p> Signup and view all the answers

    What concept explains the inheritance of traits not directly related to nucleotide sequences?

    <p>Epigenetic inheritance</p> Signup and view all the answers

    How does the presence of heterochromatin affect gene expression?

    <p>Densely condensed heterochromatin is usually not expressed</p> Signup and view all the answers

    What is primarily affected by histone modifications?

    <p>The ability of DNA to associate with histones</p> Signup and view all the answers

    What is the impact of the histone code hypothesis?

    <p>It proposes that specific modifications influence chromatin configuration and transcription</p> Signup and view all the answers

    Which type of modification is involved in long-term gene inactivation during cellular differentiation?

    <p>DNA methylation</p> Signup and view all the answers

    What happens to genes once they are methylated?

    <p>They usually remain methylated through successive cell divisions</p> Signup and view all the answers

    Why does histone deacetylation lead to reduced gene expression?

    <p>It condenses chromatin, making it less accessible</p> Signup and view all the answers

    What cellular processes can result from problems with gene expression and control?

    <p>Imbalance and diseases such as cancer</p> Signup and view all the answers

    What role do chromatin-modifying enzymes play in gene expression?

    <p>They regulate the accessibility of DNA for transcription.</p> Signup and view all the answers

    How do enhancers differ from proximal control elements?

    <p>Enhancers can be located thousands of nucleotides away from the promoter.</p> Signup and view all the answers

    What is the function of general transcription factors?

    <p>They assist RNA polymerase in the transcription of all protein-coding genes.</p> Signup and view all the answers

    Which of the following best describes alternative RNA splicing?

    <p>It produces different mRNA molecules from the same primary transcript.</p> Signup and view all the answers

    What is the role of transcription factors in the transcription initiation complex?

    <p>They interact with DNA and help RNA polymerase bind to DNA.</p> Signup and view all the answers

    How do repressors inhibit transcription?

    <p>By blocking access to the promoter region.</p> Signup and view all the answers

    Which factor is crucial for the stability of eukaryotic mRNA?

    <p>The length of the poly-A tail.</p> Signup and view all the answers

    What is the purpose of the 5' cap added during RNA processing?

    <p>It protects mRNA from exonuclease degradation.</p> Signup and view all the answers

    What significance do regulatory proteins have in alternative RNA splicing?

    <p>They identify which segments should be exons or introns.</p> Signup and view all the answers

    Which of the following statements about eukaryotic gene expression is true?

    <p>Gene expression can be influenced by chromatin structure.</p> Signup and view all the answers

    Why do eukaryotic mRNA molecules last longer than prokaryotic mRNA molecules?

    <p>Eukaryotic mRNA has a poly-A tail that stabilizes it.</p> Signup and view all the answers

    What mechanism is primarily responsible for the repression of gene expression in eukaryotes?

    <p>Chromatin-modifying proteins recruitment.</p> Signup and view all the answers

    Which statement accurately describes the transcription initiation process?

    <p>The full assembly of the initiation complex allows RNA polymerase to start moving along the DNA.</p> Signup and view all the answers

    What regulates the initiation of translation of mRNA in the cell?

    <p>Regulatory proteins binding to UTR sequences</p> Signup and view all the answers

    What triggers the activation of translation after fertilization?

    <p>Sudden activation of translation initiation factors</p> Signup and view all the answers

    Which mechanism marks proteins for degradation in the cell?

    <p>Ubiquitination</p> Signup and view all the answers

    What is a primary role of non-coding RNAs in gene expression?

    <p>To regulate gene expression</p> Signup and view all the answers

    Which group of processes leads to the development of different cell types from a single-celled zygote?

    <p>Cell division, differentiation, and morphogenesis</p> Signup and view all the answers

    What is the role of cytoplasmic determinants in early development?

    <p>To regulate gene expression affecting developmental fate</p> Signup and view all the answers

    What physiological changes occur during morphogenesis?

    <p>Changes in cell shape and motility</p> Signup and view all the answers

    Which factor is crucial for the differential gene expression in different cell types?

    <p>Different sets of gene activators</p> Signup and view all the answers

    How do some plants and algae regulate translation during periods of darkness?

    <p>By relying on light to reactivate translation</p> Signup and view all the answers

    In which way do eukaryotic polypeptides often undergo modification post-translation?

    <p>Addition of phosphate groups</p> Signup and view all the answers

    What can result from mutations that affect specific cell cycle proteins?

    <p>Resistance to proteasome degradation</p> Signup and view all the answers

    What percentage of the human genome is estimated to code for proteins?

    <p>1.5%</p> Signup and view all the answers

    How does the addition of adenine nucleotides affect mRNAs during embryonic development?

    <p>It increases their stability</p> Signup and view all the answers

    What is the process called when cells become irreversibly committed to their final fate during development?

    <p>Determination</p> Signup and view all the answers

    Which of the following statements about embryonic cell differentiation is false?

    <p>All determined cells can be placed in any location within the embryo without losing their specific fate.</p> Signup and view all the answers

    How do proto-oncogenes contribute to cancer when mutated?

    <p>They stimulate normal cell growth and division.</p> Signup and view all the answers

    What role do tumor-suppressor genes play in relation to cancer?

    <p>They repair damaged DNA and prevent mutations.</p> Signup and view all the answers

    Which gene is known for its role as a transcription factor that inhibits the cell cycle?

    <p>p53</p> Signup and view all the answers

    What mechanism can lead to the activation of oncogenes from proto-oncogenes?

    <p>Point mutations</p> Signup and view all the answers

    What is the key function of the Ras protein in relation to cell signaling?

    <p>To relay growth signals</p> Signup and view all the answers

    Which of the following best describes cancer at a cellular level?

    <p>Cells escape normal regulatory control.</p> Signup and view all the answers

    What outcome results from an increase in the copies of a proto-oncogene in a cell?

    <p>Enhanced cell cycle stimulation</p> Signup and view all the answers

    Which aspect of cell differentiation is primarily controlled at the transcriptional level?

    <p>Gene expression</p> Signup and view all the answers

    What common change occurs in cancer cells regarding chromosomes?

    <p>They have broken and rearranged chromosomes.</p> Signup and view all the answers

    During muscle cell differentiation, what specific proteins do myoblasts begin to synthesize?

    <p>Contractile proteins myosin and actin</p> Signup and view all the answers

    What triggers the excessive cell division associated with some mutations of the ras oncogene?

    <p>Hyperactive Ras protein with point mutations</p> Signup and view all the answers

    Which process illustrates how environmental factors can lead to cancer?

    <p>Point mutations in proto-oncogenes</p> Signup and view all the answers

    What is the primary function of the p53 protein when activated by DNA damage?

    <p>To act as an activator for several genes related to cell cycle regulation and DNA repair</p> Signup and view all the answers

    Which statement correctly describes the process leading to colorectal cancer?

    <p>Colorectal cancer often begins with a benign polyp that gradually accumulates multiple mutations.</p> Signup and view all the answers

    How many mutations are generally needed for a cell to become fully cancerous?

    <p>At least a half dozen mutations including oncogenes and tumor suppressor genes</p> Signup and view all the answers

    Why must mutations knock out both alleles of tumor-suppressor genes for a significant effect?

    <p>Tumor-suppressor mutations are recessive, requiring both alleles to be affected.</p> Signup and view all the answers

    What role do miRNAs activated by the p53 protein play in the cell?

    Signup and view all the answers

    Which statement accurately describes the progression of colorectal cancer?

    <p>It often starts from benign polyps that accumulate mutations.</p> Signup and view all the answers

    What must occur for a cell to become cancerous with regard to mutations?

    <p>At least one dominant mutation in an oncogene and several recessive mutations in tumor-suppressor genes.</p> Signup and view all the answers

    How does p53 contribute to preventing cancer when DNA damage is irreparable?

    <p>By inducing apoptosis via activation of 'suicide genes'</p> Signup and view all the answers

    In the context of mutations and cancer development, what is true about the mutations in tumor-suppressor genes?

    <p>Both alleles of tumor-suppressor genes typically need to be mutated for loss of function.</p> Signup and view all the answers

    Study Notes

    • Gene Expression: From Gene to Protein

      • Genes specify proteins via transcription and translation.
      • Archibald Garrod proposed "inborn errors of metabolism" linking genes to enzymes.
      • Beadle and Tatum's experiments with Neurospora crassa supported the one gene-one enzyme hypothesis.
      • Later research refined this to one gene-one polypeptide hypothesis.
      • Many eukaryotic genes produce a set of related polypeptides through alternative splicing.

      The Central Dogma

      • The flow of genetic information is DNA → RNA → protein.
      • RNA is chemically similar to DNA but uses uracil instead of thymine and ribose instead of deoxyribose.
      • Transcription is the DNA-directed synthesis of RNA.
      • Translation is the synthesis of a polypeptide using the information in mRNA.

      The Genetic Code

      • Nucleotide triplets (codons) specify amino acids.
      • There are 64 possible codons, 61 of which specify amino acids and 3 that are stop codons (no amino acid).
      • The genetic code is redundant (multiple codons can specify the same amino acid) but unambiguous (no codon specifies more than one amino acid).

      Transcription

      • RNA polymerase separates DNA strands and synthesizes a complementary RNA molecule in the 5' → 3' direction.
      • Transcription initiation, elongation, and termination are the stages of transcription.
      • Specific nucleotide sequences (promoters and terminators) signal the beginning and end of transcription.
      • In bacteria, RNA polymerase binds directly to the promoter region. Eukaryotic transcription requires transcription factors.
      • A transcription initiation complex forms, including RNA polymerase II and transcription factors.

      Eukaryotic RNA Processing

      • Pre-mRNA is modified before leaving the nucleus.
      • A 5' cap and a poly-A tail are added to the ends of the pre-mRNA.
      • Introns, non-coding regions, are removed, and exons are joined together in a process called RNA splicing.
      • Spliceosomes, consisting of snRNPs (small nuclear ribonucleoproteins), catalyze the splicing process.

      Translation

      • Transfer RNA (tRNA) is the translator, carrying specific amino acids to the ribosome.
      • tRNA has an anticodon that base-pairs with a codon on mRNA
      • Aminoacyl-tRNA synthetases attach the correct amino acid to each tRNA.
      • Wobble allows some flexibility in the base-pairing rules between the third base of the codon and the anticodon.
      • Ribosomes are the sites of translation, composed of ribosomal RNA (rRNA) and proteins.
      • Three tRNA binding sites (A, P, E) on ribosomes facilitate polypeptide synthesis.

      Translation Stages

      • Initiation: mRNA, initiator tRNA, and ribosomal subunits assemble.
      • Elongation: Amino acids are added one at a time, forming a polypeptide chain.
      • Termination: A stop codon signals the end of translation, and the polypeptide is released.
      • Multiple ribosomes can translate the same mRNA simultaneously to produce multiple copies of a polypeptide (polysomes).

      Post-Translation Modifications

      • Polypeptides fold into their three-dimensional structure after translation, aided by chaperone proteins.
      • Proteins may undergo further modifications (e.g., additions of sugars, lipids, or phosphate groups, removal of amino acids) before becoming fully functional.

      Mutations

      • Mutations are changes in DNA sequence.
      • Point mutations (substitutions, insertions, deletions) can affect protein structure and function.
      • Silent mutations have no effect on protein function.
      • Missense mutations change one amino acid to another, sometimes with little effect, sometimes with a major effect.
      • Nonsense mutations introduce a premature stop codon, generally leading to a nonfunctional protein.
      • Frameshift mutations alter the reading frame of the mRNA, causing extensive missense and often nonsense mutations.
      • Mutagens are chemical or physical agents that cause mutations.

      Gene Expression Regulation (Operons)

      • Operons are groups of functionally related genes that are coordinately controlled in bacteria.
      • The trp operon is a repressible operon, meaning it is usually on but can be turned off when the product (tryptophan) is abundant.
      • The lac operon is an inducible operon, meaning it is usually off but can be turned on when the substrate (lactose) is available.
      • Regulatory proteins (repressors or activators) bind to regulatory elements (e.g., operators) to control transcription of the operon.

      Eukaryotic Gene Expression

      • Eukaryotic genes are often regulated at various stages, including transcription initiation, splicing, and translation.
      • Chromatin structure modifications affect gene expression accessibility.
      • Histone modification (acetylation, methylation, phosphorylation) can affect chromatin condensation and gene accessibility.
      • DNA methylation also affects gene expression.
      • Epigenetic modifications can influence gene expression without altering the DNA sequence.
      • Transcription initiation involves multiple proteins including general transcription factors.
      • Promoters and enhancers are sequences that regulate gene activity through activator or repressor proteins.

      Post-Transcriptional Regulation

      • Alternative RNA splicing can yield different proteins from a single gene.
      • mRNA stability (e.g., length of the poly-A tail) affects translation.
      • Translation initiation can be blocked or promoted by regulatory proteins.

      Other Regulatory Mechanisms

      • Signaling pathways alter gene expression, particularly during development of multicellular organisms..
      • Protein modifications and degradation after translation (ubiquitination) regulate protein activity.

      Cancer

      • Cancer cells often have mutations in proto-oncogenes (stimulate cell growth) or tumor-suppressor genes (inhibit cell growth).
      • Mutations can lead to overexpression of proto-oncogenes (becoming oncogenes) or loss of function in tumor suppressors, contributing to uncontrolled cell division.
      • Multiple mutations are typically required for cancer development.

    Noncoding RNAs

    • A significant portion of the genome is transcribed into noncoding RNAs (ncRNAs) that regulate gene expression.

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    Description

    Explore the intricate processes of gene expression, including transcription, translation, and the genetic code. Understand historic theories from Garrod to Beadle and Tatum that shaped our knowledge of how genes specify proteins. This quiz covers fundamental concepts pivotal in molecular biology.

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