Phosphodiester Bonds in DNA and RNA
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Questions and Answers

What is the role of H1 in DNA packaging in eukaryotes?

  • Stabilizing both nucleosome structure and higher-order chromatin architecture (correct)
  • Linking the histone cores with linker DNA
  • Forming the histone octamer
  • Compressing and folding the 300-nm fiber
  • During mitosis, what happens to the chromosomes?

  • They wrap around the nucleosome twice
  • They form looped domains
  • They condense even further (correct)
  • They become less condensed to allow for gene expression
  • How many H2A-H2B dimers and H3-H4 dimers form the histone octamer?

  • Two of each (correct)
  • Four of each
  • One of each
  • Three of each
  • What is the purpose of the 30-nm chromatin fiber in DNA packaging?

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

    Which protein is not involved in the formation of the histone octamer?

    <p>H1</p> Signup and view all the answers

    What is the function of linker DNA in DNA packaging?

    <p>Link the histone cores with H1 protein</p> Signup and view all the answers

    In DNA packaging to produce a chromatid of a chromosome, what process follows tight coiling of the 250-nm wide-fiber?

    <p>Compressing and folding the 300-nm fiber</p> Signup and view all the answers

    What type of nucleotide substitution occurs in mRNA compared to the coding strand?

    <p>Adenine is substituted by Uracil</p> Signup and view all the answers

    Which components form the spliceosome involved in splicing pre-mRNA?

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

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

    <p>Attacks the 5’ splice site to cut the mRNA</p> Signup and view all the answers

    Where is the acceptor site located in the splicing process?

    <p>At the 3’ end of an exon</p> Signup and view all the answers

    What happens when ribonucleoprotein complexes (snRNPs) bind to exon-intron junctions?

    <p>Cutting at splice donor and splice acceptor sites</p> Signup and view all the answers

    Which sequences are recognized by spliceosomes during splicing?

    <p>GU and AG sequences at intron ends</p> Signup and view all the answers

    What is the role of spliceosomes in mRNA splicing?

    <p>Intron removal and exon joining</p> Signup and view all the answers

    What is the role of Poly(A) polymerase enzyme in mRNA processing?

    <p>Adds a poly(A) tail to the 3’ end of the pre-mRNA</p> Signup and view all the answers

    At what position downstream of the polyadenylation signal sequence does the endonuclease enzyme cleave the pre-mRNA strand?

    <p>~ 10-35 bp</p> Signup and view all the answers

    Which enzyme is responsible for cleaving the pre-mRNA strand?

    <p>Endonuclease enzyme</p> Signup and view all the answers

    What is the function of the poly(A) tail added to mRNA?

    <p>Protects mRNA from degradation</p> Signup and view all the answers

    In what manner does Poly(A) polymerase add the poly(A) tail to pre-mRNA?

    <p>Template-independent</p> Signup and view all the answers

    What is the size limit of the poly(A) tail added to pre-mRNA in mammalian cells?

    <p>~ 200 nucleotides</p> Signup and view all the answers

    Which process described is crucial for tRNA to bind to the correct sequence of mRNA during translation?

    <p>Forming hairpin loops</p> Signup and view all the answers

    What is the role of the initiator tRNA in translation?

    <p>Carrying the Met amino acid to the A-site</p> Signup and view all the answers

    What distinguishes the start codon for polypeptide synthesis?

    <p>It differentiates initiating methionyl tRNAs from internal methionine tRNAs</p> Signup and view all the answers

    Which of the following is NOT a role of the anticodon loop?

    <p>Facilitating peptide bond formation at the P-site</p> Signup and view all the answers

    Why are base substitutions sometimes not changing an amino acid?

    <p>Because of degeneracy in the genetic code</p> Signup and view all the answers

    How is the termination of an amino acid chain signaled in translation?

    <p>By one of the three nonsense or termination codons</p> Signup and view all the answers

    Where does the uncharged tRNA move after peptide bond formation?

    <p>To the E-site</p> Signup and view all the answers

    Which site on the ribosome does the empty tRNA move to after being released?

    <p>E-site</p> Signup and view all the answers

    What is the term used to describe the many non-apoptotic ways for severely damaged or stressed animal cells to die?

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

    Which process ensures that damaged or infected cells are eliminated before they can threaten animal health?

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

    How are the two original portions of each chromosome rearranged during crossing-over?

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

    Which type of cell death is associated with loss of ion gradient and tissue damage across the membrane?

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

    What is the primary cause of cell death through necrosis?

    <p>Depletion of energy</p> Signup and view all the answers

    Which pathway involves an extracellular signal leading to cell death?

    <p>Extrinsic pathway</p> Signup and view all the answers

    In which way do damaged or infected cells die to prevent a threat to animal health?

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

    What type of cell death involves an intracellular signal, often from the mitochondria?

    <p>Intrinsic pathway</p> Signup and view all the answers

    Which type of cell death is known for being a programmed process?

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

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