W2L4 - DNA packaging MCQ

• How many types of histone molecules are commonly found in eukaryotic cells?

  5 - H1, H2A, H2B, H3 and H4
• Histones have a high content of negatively charged amino acids. True or false?

  False - The histones carry a net positive charge so that they can interact with the negatively charged phosphate groups on the DNA. The histones' N-terminals tend to have many lysines and arginines in the H-terminal, which helps contribute to the positive charge.
• The association of DNA and histone is mainly mediated by?

  1. a combination of hydrogen bonds and covalent bonds
  2. covalent bonds
  3. hydrogen bonds
  4. hydrophobic interactions
  5. van der Waals interactions

  3
• With respect to histone H1 DNA packaging, which of the following applies?

  1. H1 binding gives nucleosome a defined angle
  2. H1 binds to two DNA helices at once
  3. H1 induces compaction ("30 nm fibre")
  4. H1 stabilises higher-order chromatin structures

  1, 2, 3, 4
• The chromosomes in interphase cells are highly compacted and clearly visible. True or false?

  False - In interphase, the chromosomes are not highly compacted and are clearly visible. Cells spend most of their life in interphase, so they need access to the DNA to make mRNA. If the DNA were highly compacted, then the cell would not be able to interact with the DNA easily.
• Transcription and other aspects of nucleic acid metabolism are? Which of the following apply?

  1. active in euchromatin
  2. active in heterochromatin
  3. repressed in euchromatin
  4. repressed in heterochromatin

  1 and 4
• A picture in which all of the homologous chromosomes of an organism have been stained and organised is called?

  1. chromogram
  2. chromosome panel
  3. genotype
  4. karyogram
  5. ultrasound

  4
• Chromosomes in the nucleus are highly organised

  1. All of the above
  2. all chromosomes are in defined locations in the nucleus
  3. chromosomes are ordered by importance
  4. chromosomes are ordered by size
  5. some chromosomes are in defined locations in the nucleus

  2
• A core nucleosome is composed of (choose the best answer):

  1. None of the above
  2. four copies each of histone H2A, H2B, H3 and H4 and 146 bp of DNA
  3. four copies each of histone H2A, H2B, H3 and H4 and 1470 bp of DNA
  4. two copies each of histone H2A, H2B, H3 and H4 and 146 bp of DNA
  5. two copies each of histone H2A, H2B, H3 and H4 and 1460 bp of DNA

  4
• In vitro, the rate of transcription from DNA:

  1. is higher when histones are present than when histones are absent
  2. is lower when histones are present than when histones are absent
  3. proceeds in the wrong direction unless histones are present

  2