Chromatin Structure and Heterochromatin
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Questions and Answers

What is the characteristic of euchromatin in metabolically active cells?

  • Tightly wound and highly compacted
  • Transcriptionally inactive
  • Loosely packed and diffuse (correct)
  • Rich in repetitive sequences

What is the term for the chromatin region that can transition to and from a relaxed state?

  • Facultative heterochromatin (correct)
  • Heterochromatic region
  • Euchromatin
  • Constitutive heterochromatin

What is the characteristic of heterochromatin in terms of gene expression?

  • Actively transcribed
  • Rich in repetitive sequences
  • Loosely packed and diffuse
  • Transcriptionally inactive (correct)

What is the term for the chromatin region that is always in a condensed state?

<p>Constitutive heterochromatin (A)</p> Signup and view all the answers

What is the characteristic of heterochromatin in terms of G-banding?

<p>Stains more darkly (C)</p> Signup and view all the answers

What is the term for the region of chromatin that is highly compact and shows up as dark spots in G-banding?

<p>Heterochromatin (B)</p> Signup and view all the answers

What is the primary mechanism by which rho-independent transcription termination occurs in prokaryotes?

<p>The formation of a hairpin loop structure in the RNA transcript (B)</p> Signup and view all the answers

What is the function of the rho helicase enzyme in rho-dependent transcription termination?

<p>To inactivate the elongation complex (D)</p> Signup and view all the answers

What is the role of the G:C-rich regions in rho-independent transcription termination?

<p>They are transcribed into RNA and fold into a short double-stranded hairpin (C)</p> Signup and view all the answers

What is the primary cause of transcription termination in rho-independent transcription termination?

<p>The dissociation of the elongation complex (A)</p> Signup and view all the answers

What is the characteristic of the specific sequence in the mRNA that causes transcription termination in rho-independent transcription termination?

<p>It contains inverted repeats (D)</p> Signup and view all the answers

What is the outcome of the formation of a hairpin loop structure in the RNA transcript during rho-independent transcription termination?

<p>The elongation complex dissociates (B)</p> Signup and view all the answers

What type of enzymes are small nuclear ribonucleoproteins (snRNPs) that participate in the splicing process?

<p>protein-RNA (A)</p> Signup and view all the answers

What is the function of the branch point in the splicing process?

<p>To interact with snRNA and cut the mRNA (A)</p> Signup and view all the answers

What is the sequence at the 5'-end of an intron?

<p>GU (A)</p> Signup and view all the answers

What is the function of the spliceosome in the splicing process?

<p>To remove introns from the pre-mRNA (D)</p> Signup and view all the answers

Where is the acceptor site located in the splicing process?

<p>At the 5'-end of an exon (D)</p> Signup and view all the answers

What is the result of the splicing process?

<p>The removal of an intron and the joining of exons (D)</p> Signup and view all the answers

What is the primary function of the 5' cap in eukaryotic mRNA?

<p>To protect the mRNA from 5' exonucleases (A)</p> Signup and view all the answers

What is the result of a nonsense variant in a DNA sequence?

<p>A substitution that leads to a premature stop codon (A)</p> Signup and view all the answers

What is the enzyme responsible for adding a bisphosphate group to the 5' mRNA terminal?

<p>RNA triphosphatase (C)</p> Signup and view all the answers

What is the size range of chromosomal variants?

<p>1-5 Mb (D)</p> Signup and view all the answers

During transcription of pre-mRNA in eukaryotes, what is the primary function of RNA polymerase?

<p>To elongate the transcript along the DNA template (C)</p> Signup and view all the answers

What is the result of a substitutional change from A to UAG in a DNA sequence?

<p>A nonsense mutation that introduces a premature stop codon (A)</p> Signup and view all the answers

What is the term for the unusual pyrophosphate bridge at the 5' terminus of eukaryotic mRNA?

<p>5'-5' pyrophosphate bridge (D)</p> Signup and view all the answers

What is the term for a variant that involves the duplication of a DNA sequence?

<p>Duplication (A)</p> Signup and view all the answers

What is the purpose of the methyl group added to the 7-nitrogen of guanine in the 5' cap?

<p>To provide a recognition signal for the translational apparatus (A)</p> Signup and view all the answers

What is the term for a short sequence of nucleotides that is repeated in a tandem array?

<p>Microsatellite (A)</p> Signup and view all the answers

What is the difference between prokaryotic and eukaryotic mRNA in terms of processing?

<p>Eukaryotic mRNA requires processing, whereas prokaryotic mRNA does not (C)</p> Signup and view all the answers

What is the term for a type of genetic variant that involves the insertion or deletion of one or a few nucleotides?

<p>Insertion/deletion (Indel) (C)</p> Signup and view all the answers

What is the percentage of total cellular RNA composed of tRNA?

<p>10% (B)</p> Signup and view all the answers

What is the location of the anticodon loop on tRNA?

<p>Anticodon loop is present on mRNA (A)</p> Signup and view all the answers

What is the molecular weight range of tRNA?

<p>10,000 - 31,000 (C)</p> Signup and view all the answers

What is the characteristic of the secondary structure of tRNA?

<p>Cloverleaf structure (A)</p> Signup and view all the answers

Where is tRNA predominantly located in the cell?

<p>Cell cytoplasm (C)</p> Signup and view all the answers

What is the approximate length of DNA that wraps around the core histone octamer in a nucleosome?

<p>147 bp (C)</p> Signup and view all the answers

What is the role of the H1 protein in chromatin architecture?

<p>Stabilization of both nucleosome structure and higher-order chromatin architecture (C)</p> Signup and view all the answers

What is the size of the chromatin fiber that is formed after the coiling of the 30-nm chromatin fiber?

<p>250-nm wide fiber (C)</p> Signup and view all the answers

What is the term for the stretch of DNA that links the histone cores in a nucleosome?

<p>Linker DNA (A)</p> Signup and view all the answers

How many complete turns of DNA does the 30-nm chromatin fiber make around the nucleosome?

<p>2 complete turns (D)</p> Signup and view all the answers

What is the purpose of the histone octamer in DNA packaging?

<p>To compact DNA into chromatin fibers (C)</p> Signup and view all the answers

What is the primary function of chromatin in heterochromatic regions?

<p>To silence genes by compacting them (D)</p> Signup and view all the answers

What is the characteristic of chromatin in euchromatic regions?

<p>It is loosely packed and associated with active transcription (B)</p> Signup and view all the answers

What is the difference between facultative and constitutive heterochromatin?

<p>Facultative heterochromatin is reversible, while constitutive heterochromatin is always in a condensed state (B)</p> Signup and view all the answers

What is the characteristic of repetitive sequences in heterochromatic regions?

<p>They are not transcribed and are rich in gene silencing sequences (A)</p> Signup and view all the answers

What is the relationship between chromatin structure and gene expression?

<p>Tightly wound chromatin is associated with active transcription, while loosely packed chromatin is associated with gene silencing (B)</p> Signup and view all the answers

What is the characteristic of chromatin in centromeric regions?

<p>It is tightly wound and gene-poor (A)</p> Signup and view all the answers

What is the result of the resolvase enzyme cutting at the Holliday junctions?

<p>The two original portions of each chromosome upstream and downstream from the two Holliday junctions are swapped (C)</p> Signup and view all the answers

What is the primary difference between apoptosis and necrosis?

<p>Apoptosis is a regulated process, whereas necrosis is unregulated (D)</p> Signup and view all the answers

What is the outcome of a cell that dies through necrosis?

<p>The cell is rapidly eliminated, releasing its contents and causing tissue damage (C)</p> Signup and view all the answers

What is the purpose of apoptosis in multicellular organisms?

<p>To eliminate damaged or infected cells that could threaten the health of the organism (C)</p> Signup and view all the answers

What is the characteristic of apoptosis in terms of the fate of the cell?

<p>The cell is eliminated in a controlled manner (B)</p> Signup and view all the answers

What is the primary consequence of failing to pass the G1 checkpoint in the cell cycle?

<p>Cells may be signaled to undergo apoptosis (D)</p> Signup and view all the answers

What is the primary function of the G2 checkpoint in the cell cycle?

<p>To ensure proper cell signaling for mitosis (C)</p> Signup and view all the answers

What is the consequence of a cell having damaged DNA during the G1 checkpoint?

<p>The cell undergoes DNA repair mechanisms (A)</p> Signup and view all the answers

What is the role of signals in the G1 and G2 checkpoints?

<p>To signal the cell to proceed to the next phase (C)</p> Signup and view all the answers

What is the consequence of a cell having inadequate nutrients during the G1 checkpoint?

<p>The cell arrests in the G1 phase (A)</p> Signup and view all the answers

What is the primary function of apoptosis during the cell cycle?

<p>To eliminate damaged or unwanted cells (D)</p> Signup and view all the answers

On which strand of DNA replication is synthesis continuous?

<p>Leading strand (A)</p> Signup and view all the answers

What is the location of the L-strand origin of replication in the mitochondrial genome?

<p>Outside the noncoding region, within a tRNA cluster (A)</p> Signup and view all the answers

What is the role of the mitochondrial DNA-directed RNA polymerase (POLRMT)?

<p>Initiates primer synthesis (B)</p> Signup and view all the answers

What is the primary component of nucleotides?

<p>A 5-carbon sugar (B)</p> Signup and view all the answers

What is the term for the short H-strand replication product formed by premature termination of nascent H-strand DNA synthesis at the termination-associated sequence?

<p>7S DNA (D)</p> Signup and view all the answers

What is the difference between a nucleoside and a nucleotide?

<p>A nucleotide has a phosphate group, while a nucleoside does not (C)</p> Signup and view all the answers

What is the type of sugar found in DNA?

<p>Deoxyribose (C)</p> Signup and view all the answers

How many mRNA molecules are encoded in the mitochondrial genome?

<p>13 (D)</p> Signup and view all the answers

What is the term for the process of attaching a phosphate group to a nucleoside?

<p>Phosphorylation (D)</p> Signup and view all the answers

What is the purpose of the conserved sequence boxes (CSB1-3) in the noncoding region of the mitochondrial genome?

<p>Their function is not clearly understood (C)</p> Signup and view all the answers

What is the term for the type of RNA that contains the genetic information?

<p>mRNA (A)</p> Signup and view all the answers

What is the component of nucleic acids that is responsible for the transmission of genetic traits?

<p>Nitrogenous bases (B)</p> Signup and view all the answers

What is the characteristic of the mt-rRNA and mt-tRNA molecules?

<p>They are small (D)</p> Signup and view all the answers

What is the role of the D-loop region in mtDNA?

<p>It is a regulatory region for mtDNA expression (D)</p> Signup and view all the answers

What is the source of the protein components required for mitochondrial translation?

<p>Nuclear genome-encoded genes (C)</p> Signup and view all the answers

What is the characteristic of the mtDNA genome?

<p>It is a circular DNA molecule (B)</p> Signup and view all the answers

What is the result of polyadenylation of the mRNAs in mtDNA?

<p>Generation of termination codons (A)</p> Signup and view all the answers

What is the location of the hypervariable regions in mtDNA?

<p>In the D-loop region (C)</p> Signup and view all the answers

What is the primary function of Spo11 protein in homologous recombination?

<p>To break both strands of the DNA double helix (D)</p> Signup and view all the answers

What is the role of Mre11 nuclease in homologous recombination?

<p>To degrade the ends of the broken DNA (D)</p> Signup and view all the answers

What is the outcome of the interaction between the protein-DNA filament and the sister chromatid?

<p>Formation of a double Holliday junction (D)</p> Signup and view all the answers

What is the function of DNA polymerase in homologous recombination?

<p>To extend the 3’ overhangs of the broken DNA (B)</p> Signup and view all the answers

What is the outcome of the resolution of the double Holliday junction?

<p>Generation of new genetic combinations (C)</p> Signup and view all the answers

What is the primary function of RecA protein in homologous recombination?

<p>To bind to the 3’ overhangs and form a protein-DNA filament (A)</p> Signup and view all the answers

What is the outcome of the activation of the extrinsic pathway of apoptosis?

<p>The controlled death of the cell (B)</p> Signup and view all the answers

What is the role of cytochrome c in the intrinsic pathway of apoptosis?

<p>To form a complex with Apaf1 and oligomerize into a wheel-like heptamer (B)</p> Signup and view all the answers

What is the function of the death-inducing signaling complex (DISC) in the extrinsic pathway of apoptosis?

<p>To form a complex with Fas ligand and activate the extrinsic pathway of apoptosis (B)</p> Signup and view all the answers

What is the key difference between the extrinsic and intrinsic pathways of apoptosis?

<p>The type of signal that activates the pathway (B)</p> Signup and view all the answers

What is the role of Apaf1 in the intrinsic pathway of apoptosis?

<p>To form a complex with cytochrome c and oligomerize into a wheel-like heptamer (D)</p> Signup and view all the answers

What is the outcome of the cleavage of key proteins by the executioner caspases in the apoptosis pathway?

<p>The cell dies in a controlled manner (B)</p> Signup and view all the answers

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