Molecular+Biology+3

Sue, Peggy, Kim and Kathy
 * Assessment Items from the Molecular Biology 3 Small Group**
 * Alignment table**
 * **Learning goal:**
 * **Learning goal:**


 * In the context of modern molecular biology, explain cellular information transfer using the central dogma.** || **Intended outcome:**


 * Student will be able to explain or illustrate the central dogma, including 2-3 current known exceptions or extensions.** || **Assessment**


 * Students will**


 * 1 Formative assessment**
 * *See column **
 * at right **


 * 2 Summative assessments**

**Essay questions below** || **Learning activity (Formative assessment**


 * Work in groups . *Part I: Beginning with the words “DNA” RNA” and “Protein”, create a concept map illustrating the central dogma. Part II: Include (2-3) extensions or exceptions to the central dogma in the context of modern molecular biology. Title this concept map and justify why your title is a more appropriate than “The Central Dogma” ** ||

.
 * Essay Question 1:** You are woken in the night by the cries of a distressed kitten at your dorm window. You bring the kitten to the vet for immediate care. The vet informs you that the kitten is not in immediate danger, but unfortunately, has tested positively for Feline Immunodeficiency Virus (FIV), a retrovirus. Diagram the flow of intracellular information from the virus that enters the cell to the virus that leaves the cell. Explain why this would be considered an exception to the Central Dogma.


 * Sample Answer: (added by kmarrs)**

DNA --> RNA --> Protein
 * Flow of information in the traditional 'Central Dogma':**

Retroviral entry -- > Reverse Transcription of viral genome in cytoplasm --> generation of DS DNA and LTRs --> Nuclear Translocation --> Integration into Genome --> Transcription --> Splicing --> ....and subsequent translation of capsid proteins + packaging of progeny RNAs into viral capsids.
 * Flow of information in FIV (HIV, etc):**

" The effect of retrovirology on our concept of genetic information, its molecular forms, transmission, and evolution has been nothing short of revolutionary. In the early years of molecular biology, no exceptions to the unidirectional and presumed irreversible flow of genetic information from DNA to RNA to protein were known. This unidirectional flow came to be known as the “Central Dogma.” I**t was this Central Dogma that had to be revised when the replication of retroviruses was understood**: The retrovirus growth cycle includes as an essential step the copying of RNA into DNA by a virus-coded polymerase, reversing the flow of genetic information, hence the terms “retroviruses” and “reverse transcriptase”. The hallmark of retroviruses is a replicative strategy that includes as essential steps reverse transcription of the viral RNA into linear double-stranded DNA and the subsequent integration of this DNA into the genome of the cell." http://www.ncbi.nlm.nih.gov/books/NBK19382/ http://www.ncbi.nlm.nih.gov/books/NBK19382/figure/A21/?report=objectonly


 * Essay Question 2: Explain or Illustrate how the process of Prion Infection represents cellular information transfer bypassing critical steps of the central dogma.**

Prions are infectious proteins that propagate themselves via conformational changes in other molecules of the same type of protein.
 * Sample answer (added by kmarrs)**

PrPS (scrapie form) --> PrPS (scrapie form) + PrPC (cellular form) -> PrPS + PrPS (conversion to scrapie form)
Prion entry ( PrPS, prion/scrapie form) --> triggers an induction of existing, endogenous properly folded proteins PrPC (cellular form) into the disease-associated, prion form. The prion acts as a template to guide the misfolding of more protein into prion form. The accumulating newly formed PrPS prions then induce additional conversion of endogenous PrPC --> scrapie form PrPS, triggering a chain reaction that produces large amounts of the PrPS prion form.

"Prior to the discovery of prions, it was thought that all organisms used nucleic acids to direct replication. The "protein-only hypothesis" states that a protein structure can replicate without the use of nucleic acid. **This was initially controversial as it contradicts the Central Dogma**, which describes nucleic acids as the central form of replicative information." Baker & Ridley (1996). //Prion Disease//. New Jersey: Humana Press. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2933051/