Question

19) Core Concept: Information Flow- Explain how information from DNA results in the synthesis of a protein. Explain how information in the environment ultimately results in changes to gene expression.

20) Explain the steps in DNA recombinant technology (FROM GFP LAB). Include restriction enzymes, plasmids, heat shock, transformation and names of any enzyme that is needed in your answer.

21) Explain the purpose and/or what is happening at any step in the GFP lab protocols.

22) Predict how defects in the regulation of cell-cycle checkpoints would affect cells and explain how these defects relate to uncontrolled division in cancer and cancer progression.

Answer 1

Answer: (19)

In bacteria, archaea, and eukaryotes, the primary role of DNA is to store heritable information that encodes the instruction set required for creating the organism in question. While we have gotten much better at quickly reading the chemical composition (the sequence of nucleotides in a genome and some of the chemical modifications that are made to it), we still don't know how to reliably decode all of the information within and all of the mechanisms by which it is read and ultimately expressed.

There are, however, some core principles and mechanisms associated with the reading and expression of the genetic code whose basic steps are understood and that need to be part of the conceptual toolkit for all biologists. Two of these processes are transcription and translation, which are the coping of parts of the genetic code written in DNA into molecules of the related polymer RNA and the reading and encoding of the RNA code into proteins, respectively.

In BIS2A, we focus largely on developing an understanding of the process of transcription (recall that an Energy Story is simply a rubric for describing a process) and its role in the expression of genetic information. We motivate our discussion of transcription by focusing on functional problems (bringing in parts of our problem solving/design challenge rubric) that must be solved the the process to take place. We then go on to describe how the process is used by Nature to create a variety of functional RNA molecules (that may have various structural, catalytic or regulatory roles) including so called messenger RNA (mRNA) molecules that carry the information required to synthesize proteins. Likewise, we focus on challenges and questions associated with the process of translation, the process by which the ribosomes synthesize proteins.

The basic flow of genetic information in biological systems is often depicted in a scheme known as "the central dogma" (see figure below). This scheme states that information encoded in DNA flows into RNA via transcription and ultimately to proteins via translation. Processes like reverse transcription (the creation of DNA from and RNA template) and replication also represent mechanisms for propagating information in different forms. This scheme, however, doesn't say anything per se about how information is encoded or about the mechanisms by which regulatory signals move between the various layers of molecule types depicted in the model. Therefore, while the scheme below is a nearly required part of the lexicon of any biologist, perhaps left over from old tradition, students should also be aware that mechanisms of information flow are more complex (we'll learn about some as we go, and that "the central dogma" only represents some core pathways).