DNA vs. Protein Debate-Which is the Hereditary Material?

DNA Quiz:


DNA Replication Video
Article about Crick's Letters

DNA Timeline & Applications

Biotechnology Techniques

Introduction to/Applications of Biotechnology

DNA Replication

DNA Structure

Protein Synthesis Questions

Biotechnology Tools and Techniques Lesson Assignment

Restriction Endonucleases
Mariam and Courtney
Methylases and DNA Ligase
Chris and Brittney
Gel Electrophoresis
Aleena and Federico
Polymerase Chain Reaction
Sarah & Sarah
Restriction Fragment Length Polymorphism
Clinton and Drew
Genetic Engineering/DNA Cloning
Marshell and Tom
Leila and Eva
DNA Sequencing
Mimi and Joanne
Plasmids & Mapping
Scott, Fiona and Sangitha
Chapter 4: Genetics - Section 4.1 - By Drew MacNeil
November 24, 2010

In-class animation, “Debate: Is the hereditary material protein or DNA?”: http://www.dnaftb.org/dnaftb/15/concept/
  • Protein considered to have higher chance of being the genetic material due to it’s potential for variation (they produced enzymes and were composed of polymers of 20 different amino acids).
  • DNA was simple, with only 4 different nucleotide possibilities.
  • Friedrich Miescher: isolated substance called nuclein from the nucleus of pus cells.
  • Nuclein was high in phosphorus; he thought it was the phosphorus storehouse of the cell (although it is actually DNA).
  • Phoebus Levene found that nuclein contained proteins and amino acids and 2 nucleic acids (now known as DNA and RNA).
  • DNA contains 4 differnet nucleotides (A,C,G,T), each with a phosphate group, deoxyribose sugar, and nitrogenous base.
  • Phosphate group bonds between the hydroxyl group on carbon five of one sugar to carbon three of the next, forming the DNA backbone.
  • DNA directionality is said to be from 5’ to 3’.
  • DNA was thought to repeat in the same order, with the same amount of each base, called tetranucleotides (A-C-G-T).

external image dna_structure.gif
Picture obtained from: http://evolution.berkeley.edu/evosite/history/images/dna_structure.gif

For more on DNA structure, see this interactive site: http://www.johnkyrk.com/DNAanatomy.html

Reference to the textbook, section 4.1 (page 206) and here: http://www.accessexcellence.org/RC/VL/GG/hammerling_s.php
  • Joachim Hammerling experimented with Acetabularia, which was easily seen (each cell was 5cm long).
  • He removed the caps of some cells, and the feet from others (which contained the nucleus).
  • The ones that had their heads removed regenerated; the feet did not.
  • Two acetabularia species were then used, each with a different cap.
  • He grafted the stalk of one species onto the foot of the other species.
  • A new cap grew; first it was a mix of both species but when that was cut off, a new one regenerated that was purely the same species of the foot.
  • The genetic material is found in the nucleus.

In-class animation, “A gene is made of DNA”: http://www.dnaftb.org/dnaftb/17/concept/index.html
  • Griffith’s transforming principle: DNA can become virulent if exposed to dead virulent DNA.
  • Griffith used 2 pneumococcus strains: R (not virulent) and S (virulent - has sugar coat to protect from immune system).
  • Mouse died if exposed to S, lived if exposed to R.
  • In a person, both strains could be found; he wanted to see if one could turn into the other.
  • Griffith used heat to kill the S strain; not virulent anymore.
  • Mixed dead S strain with live R strain; mouse died; he isolated live S from this mouse’s blood and found that it could infect other mice too.
  • He dictated that some “principle” transformed the R strain into the S strain.
  • McCarty, MacLeod, and Avery then heat killed the S strain and used detergent to split it open - obtained debris and Lysate.
  • Lysate consisted of protein, DNA, RNA, and sugar coat remnants.
  • Lysate combined with R cells produced S cells.
  • SIII enzyme used to remove sugar coats from lysate; remaining substance still produced S cells from R cells.
  • Proteinase used to remove proteins from lysate now; remaining substance only consisted of DNA and RNA - this substance still produced S cells from R cells.
  • The two nucleic acids were then isolated and were tested for transforming ability; they transformed R into S.
  • RNA was then destroyed in this substance using RNAase (only DNA left); could still transform R into S.
  • Used DNAase to remove all DNA (nothing left in solution now); it was unable to transform R into S.
  • R could not transform into S without DNA! DNA is the transforming principle.
external image 450px-Griffith_experiment.svg.png
Picture obtained from: http://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/Griffith_experiment.svg/450px-Griffith_experiment.svg.png

Hershey-Chase experiment animation: http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#
  • They experimented with bacteriophages (which consist of DNA and protein).
  • Some bacteriophages were grown in the presence of S-35 radioactive sulfur (sulfur is only found in the protein portion).
  • These bacteriophages infected bacterial cells; no radioactive sulfur was found in the newly grown bacteriophages.
  • Other bacteriophages were grown in the presence of P-32 radioactive phosphor (phosphor is only found in the DNA portion).
  • These bacteriophages infected bacterial cells; radioactive phosphor was found in the newly grown bacteriophages.
  • This is concrete evidence that DNA is the hereditary material, not protein.
external image hersheychase.gif
Picture obtained from: http://www.sciencegateway.org/resources/biologytext/dogma/images/hersheychase.gif

An article all about the debate of DNA vs. protein was also mentioned in class: http://www.nature.com/scitable/topicpage/Isolating-Hereditary-Material-Frederick-Griffith-Oswald-Avery-336

Hey Guys,

Here is my powerpoint from the lesson on PCR (Polymerase Chain Reaction). Feel free to go over it, and I also suggest that you watch the narrarated animation for yourself; I found it really helped. Here is the link for that: http://www.sumanasinc.com/webcontent/animations/content/pcr.html

Anyways, if you guys have any questions about PCR at all you can post them here and I can try to answer them, or you can also message me.


Plasmid animation


Here is a copy of the Handout.


DNA Sequencing
Most of the information is written in the notes section of the Powerpoint.

This animation also offers a better understanding of the Sanger dideoxy method of DNA sequencing :

DNA Fingerprinting Lab:

Way to Glow Lab: