Genetics Exam 4

• What are the three levels of DNA structure

  primary, secondary, tertiary
• primary structure=

  nucleotide sequence
• secondary=

  double helical structure
• tertiary structure=

  folding of double helix to fit into the cell
• prokaryote


  before + nucleus = bacteria
• eukaryote

  true + nucleus = most plants and animals
• • genome: usually one circular DNA molecule, DNA: not complexed with histones in eubacteria; some histones in archaea, amount of DNA: relatively small


  prokaryotic cells
• • genome: multiple linear DNA molecules, DNA: complexed with histones, amount of DNA: relatively large

  eukaryotic
• Bacterial Chromosome Structure: one circular chromosome = 


  one DNA molecule
• In bacterial chromosome structure, relaxed DNA is significantly _____ than the ______________


  longer; volume of the cell
• What shape of chromosomes can be supercoiled?

  circular
• DNA without a free end will __________ B DNA will twist to the ______

  twist up on itself; left (negative supercoil)
• What structure is the following describing: single DNA molecule, usually one big circle, DNA is looped-proabably anchored by protein, clumps in cell in one place= nucleoid

  prokaryote chromosome structure
• T/F: DNA is highly folded to form the chromosome structure.

  T
• DNA + Protein

  chromatin
• T/F: Each sister chromadid is a RNA molecule.

  F: DNA
• Put the steps in eukaryotes compacting DNA in order. 1. Loops are condensed into chromatin fibers2.The nucleosomes are then supercoiled to form solenoids3. Solenoids form loops on a non-histone scaffold4. DNA is wound up on nucleosomes

  4>2>3>1
• histones

  very basic proteins (positively charged), highly conserved among all eukaryotes, present in most cell types, essential for compacting the DNA, may play a role in activating or silencing regions of DNA
• What are the five histone proteins?

  H1 (outside the nucleosome), H2a, H2b, H3, H4 (inside the nucleosome)
• How much nucleotide pairs of DNA are wrapped around a histone octomer?


  145-147
• How are nucleosomes compacted and wound into solenoid structures?

  by the addition of histone H1
• What is the first step of the movement of replication fork past nucleosomes?

  nucleosome partially dissasembles into two half-nucleosomes
• What is the second step of the movement of replication fork past nucleosomes?

  fork replicates past half-nucleosomes
• What is the third step of the movement of replication fork past nucleosomes?

  nucleosomes reassemble from old half-nucleosomes and newly sythesized histones
• T/F: Nucleosomes also replicate semi-conservatively.

  T
• What is the unique role of the telomere?

  protect the ends of the DNA molecule from unraveling or from degrading; special problems in replication
• Vertebrate telomere repeate sequence:

  5'-TTAGGG-3'
• What creates a cap at the end of the chromosome?

  a G-rich single-stranded run at the very end that folds back and bonds with itself
• Telomeres form caps at the end of a chromosomes that contain ______?

  a unique DNA sequence that is repeated several times
• T/F: The DNA sequence varies slightly between species.

  T
• Special repeat sequences make up the ______

  telomere
• Telomeres can be labeled using the _________

  repeat sequence
• What are the criteria for genetic material?

  store information, replicate, express information, allow variation by mutation
• In semi-conservative replication of DNA, each DNA molecule formed is _______?

  1/2 old, 1/2 new
• What are the 3 possible models of DNA replication?

  semiconservative replication, conservative replication, dispersive replication
• What experiment showed that DNA replicates by a semi-conservative method where the products of DNA replication are 1 new DNA strand paired with 1 fully new DNA strand?

  Meselson & Stahl experiment
• What are the requirements of replication?

  a template consisting of single stranded DNA, raw materials to be assembled into a new nucleotide strand, proteins that read the template and assemble the substrates into a DNA strand
• What are the four stages of replication in prokaryotes (E.coli)?

  initiation, unwinding, elongation, termination
• How many origins do bacteria and viral chromosomes typically have?

  one
• T/F: Eukaryotes replicate their DNA from multiple origins. There are multiple origins on individual chromosome.

  T