Chapter 14 / LAB (BIO 1306)

• Nitrogenous bases for RNA?

  Adenine

  Guanine

  Uracil

  Cytosine
• Nitrogenous bases for DNA?

  Adenine

  Guanine

  Thymine

  Cytosine
• What is the 3-dimensional structure of DNA?

  5-carbon sugar

  A phosphate group

  nitrogenous base
• what are the 5 carbon sugars made of?

  deoxyribose in DNA

  ribose in RNA
• What are the nitrogenous bases made of?

  purine or pyrimidine
• transformation

  the uptake of DNA directly from the environment; a natural process in some bacterial species.
• what are the properties of the substance (Avery, MacLeod, McCarty) that resembled DNA?

  1. Elemental composition matched DNA
  2. Similar density in ultracentrifugation
  3. chemical resistance- lipids and proteins
  4. enzyme resistance-proteins and RNA
  5. Enzymes that break down DNA destroyed transforming activity
• Hershey & Chase discovered what?

  DNA is the genetic material injected by virus and responsible for viral replication (built on Avery, M, M)
• Which phage only contained DNA? (Hershey)

  Radioactive Phosphorus 32P
• Which phage only contained protein? (Hershey)

  Radioactive Sulfur 35S
• What did experiment 1 test? (Hershey)

  Phage growth in 32P (DNA)
• What did experiment 2 test? (Hershey)

  Phage growth in 35S (protein)
• Results of 32P EXP.

  High levels of radioactivity found in the cell pellet.
• Result of 35S EXP.

  Low levels of radioactivity found in the cell pellet.
• which chromosomal entities are an individual's traits specified?

  genes
• phosphodiester bond

  ester bonds that form between sugar and phosphate to form the backbone of nucleic acids.
• X-ray diffraction

  involves passing an x-ray beam through a crystalline DNA and projecting it onto a screen.
• repeating sugar and phosphate units in a single DNA strand make up the...

  phosphodiester backbone
• transforming substance isolated by Avery, MacLeod and McCarty..

  • The elemental composition of the substance was very similar to that of DNA.
  • Protein-digesting enzymes did not affect its transforming ability.
  • RNA-digesting enzymes did not affect its transforming ability.
  • DNA-digesting enzymes destroyed its transforming ability.
• Watson and Crick's model of DNA consisted of

  1. double-helix structure of 2 strands twisted around each other
  2. a backbone composed of alternating deoxyribose sugars & phosphate groups
  3. an interior of nitrogen bases that complementary pair with each other through hydrogen bonds ( A-T | C-G )
• complementary


  Describes genetic information in which each nucleotide base has a complementary partner with which it forms a base-pair.
• antiparallel configuration

  run parallel to each other but with opposite directionality (alignments.)
• Watson and Crick Model includes

  • sugar phosphate backbone
  • double stranded structure
  • a helical structure
  • sequence of bases on the 2 strands is complimentary
  • each strand is polar
  • 5' and a 3' end
  • antiparallel direction
• X-ray diffraction concluded that the diameter of a DNA molecule is...

  2nm
• the DNA backbone is composes of...

  phosphate groups

  sugars
• conservative model (Meselson and Stahl)

  • parental strands stay intact
  • new DNA copies are entirely new molecules
  • outcome: both daughter strands are completely new
• semiconservative model (Meselson and Stahl)

  • one parental strand remains in each daughter molecule
  • new complementary strand is synthesized for each parental strand
  • outcome: each daughter molecule has 1 parental strand & 1 new strand
• dispersive model (Meselson and Stahl)

  • DNA copies are a mix of parental and new strands
  • new DNA is scattered throughout each strand in both daughter molecules
  • outcome: both daughter strands have segments of parental & new DNA
• conservative model

  produces one entirely new molecule and conserves the old one

  
• semiconservative model

  produces two hybrid molecules of old and new strands

  
• dispersive model

  produces hybrid molecules with each strand a mixture of old and new

  
• Meselson-Stahl experiment

  tested the possible models of DNA replication by growing bacteria in a heavy isotope of Nitrogen (15N), transferring it to light nitrogen, and spined it.
• Basic mechanism is semiconservative replication, what occurs?


  DNA helix opens up

  copies of both strands are made

  two daughter helices are formed

  daughter strands: 1 original and 1 new
• What are 3 things replication requires?

  1. something to copy - parental DNA molecule
  2. something to do the copying - enzymes
  3. building blocks to make the copy - nucleotide triphosphates
• What is the biochemical process for replication?

  initiation

  elongation

  termination
• helicase

  Any of a group of enzymes that unwind the two DNA strands in the double helix to facilitate DNA replication.
• single-strand binding protein (SSB)

  coats and stabilizes single-stranded DNA
• what enzyme prevents supercoiling?

  DNA gyrase
• leading strand

  continuous synthesis from a single primer
• lagging strand

  discontinuous synthesis with multiple primers