Types of genetics, early experiments, & DNA structure
Supplemental Instruction
IowaStateUniversity / Leader: / Matt C.
Course: / Biol/Gen 313
Instructor: / Dr. Myers & Dr. Vollbrecht
Date: / 01/17/2017

Introduction: This worksheet discusses material covered in the first and second lectures (01/09/17 and 01/11/17). Chapters 1 and 8 examine these topics.

Concepts

  1. Subdisciplines of genetics.
  2. Experiments that provided the identity and characteristics of genetic material.
  3. DNA characteristics and structure.

Material

  1. Subdisciplines of genetics.

In class we briefly discussed the difference between the subdisciplines of genetics. These included molecular, transmission, and population genetics. In the following cases, choose which subdiscipline you think best contains the stated research and briefly explain why.

  1. A researcher follows the evolution of lactose tolerance in human societies that domesticated cattle.
  1. A researcher recognizes distinct motility alleles differentiating virulent and non-virulent bacteria, and attempts to find genetic markers for the allele.
  1. Researchers analyzing the prevalence of increased beak depth in groups of finches on the Galápagos in relation to available seed size.
  1. A researcher investigates European royal lineages and the inheritance of hemophilia therein.
  1. A research group documents the proliferation of methicillin-resistant Staphilococcus aureus (MRSA) strains in hospital environments.
  1. Researchers study the process of histone modification.
  1. A researcher works to better describe the mechanism of crossing over during meiotic cellular division which leads to mutant phenotypes in offspring.
  1. A litter of puppies is verified to be purebred.
  1. A researcher uses genetic markers to advise an apple farmer on crosses to make to produce offspring that produce sweeter fruits.
  1. Experiments that provided the identity and characteristics of genetic material.

Dr. Myers discussed three experiments in lecture that may appear on tests in a capacity that requires more thorough understanding, however; there are a few discoveries that may be featured in memorization-focused multiple choice questions. Study these by yourself; know these scientists’ contributions: Friedrich Miescher; Albrecht Kossel; Phoebus Aaron Levene;Maurice Wilkins, Rosalind Franklin, James Watson, and Francis Crick.

  1. Fred Griffith’s experiment:
  1. Griffith found that there was a “transforming principle” that could confer virulence from a dead virulent strain of bacteria to a living non-virulent strain. Describe how he tested for the identity of this transforming principle. (Feel free to diagram it.) (Avery, MacLeod, and McCarty verified this work.)
  1. What would be the results of the experiment have been if RNA was the transforming principle?
  1. What would be the conclusion if DNase (an enzyme that cleaves DNA) and RNase both had prevented transformation?
  1. Alfred Hershey and Martha Chase’s experiment:
  1. Hershey and Chase knew that viruses – which are made of protein and DNA – somehow passed on genetic information into their host, but didn’t know what chemical contained the genetic information. Describe their experiment and what happened.
  1. What conclusion would you draw if radioactive sulfur isotopes (labelled protein) were found in the bacteria?
  1. What conclusion would you draw if both radioactive isotopes ended up in the bacteria?
  1. Erwin Chargaff’s experiment:
  1. Chargaff tested for A, T, C, and G concentrations in double-stranded DNA. What were his findings? (Chargaff’s rules.)
  1. What conclusion would you draw if [A] = [C] and [T] = [G]?
  1. What conclusion would you draw if [A] = [C] = [T] = [G]? (Is there a proposed theory that applies here?)
  1. What can you tell about the following nucleic acid samples?
  2. Double-stranded DNA; [A] = 21%
  1. Double-stranded RNA; [G] = 15%
  1. Unknown nucleic acid; [C] = 30% and [U] = 25%
  1. Unknown nucleic acid; [T] = 30% and [G] = 25%
  1. DNA characteristics and structure.
  2. Sketch a model of a DNA nucleotide in a nucleic acid polymer. Include the following elements: numbering of carbons on the sugar; an indication of which carbon you’ll look at to differentiate DNA from RNA; where the phosphodiester backbone is; an indication of charge and its sign on relevant components. You do not have to include a specifically drawn base.
  1. Describe the difference between a purine and a pyrimidine.
  1. Name the bases pictured below.
  1. Indicate on one of the above bases a position that is sp3 hybridized (pyramidal or tetrahedral) and one that is sp2 hybridized (flat or planar).

Things to do next

  • Focus your review on things that were difficult from this worksheet. If it was really challenging, don’t worry; these are meant to be tough and push your understanding of the topics we covered.
  • Study up on the scientists mentioned in Concept 2. Not too much can be asked about them beyond what you’ll know from rote memorization. Their contributions are significant, but it’s tough to frame their work in a way that would push you to think deeply.
  • If you have any questions, ask me in session, in class, or by email. I’m more than happy to help.
  • Next session (Thursday 01/19/17) we’ll be talking about the material from the third and fourth lectures (01/13/17 and 01/18/17). These will include more detail on DNA structure focused on bonding, higher order chromatin and chromosome structures, and material from the fourth lecture.