Unit 8: Protein Synthesis: How Genes are Expressed in the Cell
Reading
BJU Biology: Ch. 4B - "Cell Metabolism and Protein Synthesis", and Ch. 7 "Biotechnology"
AP Classroom: Unit 6 - "Gene Expression and Regulation"
Topics
Examples of genetic engineering:
Labs
BJU Biology: Ch. 4B - "Cell Metabolism and Protein Synthesis", and Ch. 7 "Biotechnology"
AP Classroom: Unit 6 - "Gene Expression and Regulation"
Topics
- Transcription & translation
- Gene expression and regulation
- Biotechnology
- "Human Insulin Report"
Examples of genetic engineering:
- Gene therapy - Gilead Science's Car T-cell therapy (Kymriah & Yescarta) for Leukemia - review the cost!!
- Insulin production - from Banting & Best's original patent to Genentech and Ely Lilly making recombinant 'human' insulin
- DNA Fingerprinting - uses PCR, restriction enzymes, and gel electrophoresis
- Agricultural applications - Monsanto's Roundup Ready "RR" corn, and Bt corn & cotton
Labs
- In-class: "From DNA to Protein Structure & Function"
- Virtual: Transgenic Fly Lab
What are we learning here?
It is often said, "DNA makes RNA, RNA makes proteins, and proteins make you".
This is partly true.... your DNA does contain the instructions for at least the 'base set' of proteins. However, we have known for at least 30 years that the Body Plan of organisms is not solely determined by DNA, and the carbohydrate signaling molecules contained in the cell membrane contain more information than proteins, and most RNA goes through a lot of post-transcriptional editing independent of DNA. Therefore, it's not completely accurate to say "proteins make you".
Consider: You also have a mind - that is to say, you have volition and a will. In other words, you are not just a machine made out of meat. You are also a product of your will and your decisions. You can make good and bad decisions that will affect your life. Blaming your DNA for everything is called "Environmental Determinism" - and to be happy and fulfilled in life you want to try to avoid doing that. So we need to look at DNA for what it is - simply one of the sources of information for proper protein-construction.
Step 1: Transcription
It is often said, "DNA makes RNA, RNA makes proteins, and proteins make you".
This is partly true.... your DNA does contain the instructions for at least the 'base set' of proteins. However, we have known for at least 30 years that the Body Plan of organisms is not solely determined by DNA, and the carbohydrate signaling molecules contained in the cell membrane contain more information than proteins, and most RNA goes through a lot of post-transcriptional editing independent of DNA. Therefore, it's not completely accurate to say "proteins make you".
Consider: You also have a mind - that is to say, you have volition and a will. In other words, you are not just a machine made out of meat. You are also a product of your will and your decisions. You can make good and bad decisions that will affect your life. Blaming your DNA for everything is called "Environmental Determinism" - and to be happy and fulfilled in life you want to try to avoid doing that. So we need to look at DNA for what it is - simply one of the sources of information for proper protein-construction.
Step 1: Transcription
- This is the process of copying DNA to make mRNA (messenger-RNA).
- When you transcribe something, you copy it. A "scribe" is someone who makes copies of things. Thus, transcription is copying the DNA to make a strand of RNA.
- This is where the mRNA travels outside the nucleus and assembles a sequence of amino acids into specific proteins. The mRNA is like a Post-It Note, carrying the genetic instructions out of the nucleus (the central office) into the endoplasmic reticulum (the assembly area); finding a ribosome (a work station), loading itself into the infeed slot (like a tape reader), being read - 3 bases at a time - by the ribosome, matching-up a tRNA with every 3-base codon (like a factory assembly-jig), having a specific amino acid attached to the other end of each tRNA in the lineup (like a bunch of subassemblies attached to robot arms), resulting in a string of amino acids becoming attached to one another in a predefined sequence, and that string of amino acids (called a polypeptide at this point) gradually folding-up into a very specific predefined shape, and then moving off to a 2-part folding machine (known as a chaperonin), wherein it is carefully folded into its final shape necessary for whatever purpose the protein serves.
- When you translate something, you write it in a different language. The language of mRNA uses a 4-letter alphabet (the A-U-C-G bases we have been talking about), while the language of proteins uses a 20-letter alphabet (the 20 amino acids we have talked about). Thus, it literally is translating the genetic code from one language into another!
- Thus, the tRNA (transfer RNA) serves as the "dictionary", or Rosetta Stone. If you don't know what the Rosetta Stone was, it was an ancient slab of stone (a "stele") covered with official writing in 3 languages, discovered in 1799, which cracked the ancient language of Egyptian hieroglyphics - which had been a mystery until that time! Transfer RNA serves as the translator between the language of RNA and the language of polypeptides.
- If you think about it, you begin to realize that the information is primary in this whole, fascinating process. It doesn't matter what group of molecules is being used; the information stays primary! Here's an example: I can think of an idea in my mind, write it down on a piece of paper, type it into my laptop, hit a button and send it via radio signals to a box on the wall, the box sends it as pulses down a cable, a radio tower down the street sends it using radio frequency, and someone on the receiving end then goes through the exact process in reverse. In this example, I have used many different mediums to express and store information - but the information is primary!...and had to come from somewhere outside the system I just described. The exact same thing is going on with information in the cell. The information (the computer code) is primary, and thus it had to come from somewhere outside the cell.
- A gene is simply a section of DNA which encodes for a protein. This is important, and puzzles many students. A gene isn't a "compartment in the cell"! It's just the term we use for a protein-encoding section of DNA... it may be 200 base pairs long, or may be thousands of base pairs long.
- You have around 25,000 genes located on your 46 chromosomes. Mapping various genes and figuring out what they make is what you do in medical research.
- These do most of the work in the cell; they form structural elements, signaling molecules, enzymes, and complex machinery of the cell.
- We keep discovering new proteins all the time. You may have as many as 200,000 different types of proteins (the number keeps getting bigger as new proteins are discovered).
- When a newly-manufactured RNA emerges, it is edited to remove "introns" (non-coding regions that you don't want) and keep "exons" (coding regions that you do want).
- Memory device: EXons are EXpressed, and INtrons are IN-between.
- The way the RNA is edited determines what protein it ends up making.
- Because of RNA splicing/editing, each gene is able to make more than one protein! So we no longer say, "One gene, one protein".
| Lecture Slides: Protein Synthesis |
| 11._gene_regulation_slides.ppt |
Video clips below: We will watch and discuss in class
Homework
Starting 2022, the Gene Expression homework is hosted in Canvas as a multiple choice exercise. Check Canvas for the due date.
Starting 2022, the Gene Expression homework is hosted in Canvas as a multiple choice exercise. Check Canvas for the due date.
Transgenic Fly Lab (virtual)
www.biointeractive.org/classroom-resources/transgenic-fly-virtual-lab
Instructions:
www.biointeractive.org/classroom-resources/transgenic-fly-virtual-lab
Instructions:
- Go to the link, click on "launch interactive", and complete the lab.
- Take the embedded quizzes.
- Turn-in your responses to the quizzes. (Group them together and turn them in via email).
Human Insulin report
| 12._human_insulin_report_2023.docx |
| insulin_paper_-_STUDENT EXEMPLAR.pdf |
| 12._insulin_history_11_slides_excellent.pdf |
| 12._insulin_and_diabetes_history_24_slides_excellent.pptx |
| 3._diabetes_ppt_-_very_good.pptx |