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Mini-Lectures Below
Lessons
Lesson 1: From Gene to Protein – Building CFTR
Remember CFTR from our last module? That finicky protein channel that causes cystic fibrosis when it doesn’t work? Well, here’s the million-dollar question: how does your body actually MAKE CFTR in the first place? We’re about to trace the journey from a recipe written in DNA all the way to a functional protein sitting in your cell membrane. Spoiler alert: it involves copying, translating, and a whole lot of molecular machinery that would make a factory jealous.
Think about it this way: your cellsThe basic structural and functional units of life. have been making CFTR proteinsLarge molecules made of amino acids with various functions in the body. since before you were born. Every single respiratory epithelial cell in your airways contains the CFTR gene on chromosome 7, and that gene gets read thousands of times to produce the proteins you need. The process is called protein synthesis, and it’s happening in your body right now as you read this. Today we’re going to follow the step-by-step instructions that turn a sequence of nucleotidesThe building blocks of nucleic acids. (DNA) into a sequence of amino acids (protein), and you’ll see exactly where things go wrong in cystic fibrosis.
Key Concepts:
- DNA Structure as Information Storage – The CFTR gene is a specific sequence of nucleotides on chromosome 7 that contains the instructions for building the CFTR protein
- Transcription: DNA → RNA – Making a disposable mRNA copy of the CFTR gene that can travel from the nucleusThe control center of the cell that contains DNA and directs cellular activities. to the ribosomesSmall structures responsible for protein synthesis, either free-floating or attached to the rough ER
- Translation: RNA → Protein – Ribosomes read the mRNA sequence and assemble amino acids in the correct order to build the CFTR pro
Pre Class Lectures
- DNA Structure 12 minutes
- DNA to RNA (Transcription) 13 minutes
- RNA to Protein (Translation) 17 minutes
Post Class Lectures
- The Cell Cycle 15 minutes
Lesson 2: DNA Replication – Copying the CFTR Recipe
Your body makes about 25 million new cells every second. That’s 25 million times per second that your DNA needs to be copied PERFECTLY, including the CFTR gene on chromosome 7. One copying mistake in the CFTR gene, and boom—you might have a daughter cell that can’t make functional CFTR protein. So how does your body pull off this miracle of precision copying? And more importantly, what happens when it doesn’t?
Here’s the thing about DNA replication: it has to be both incredibly fast and incredibly accurate. Your cells use an enzyme called DNA polymeraseAn enzyme that synthesizes new DNA strands by adding nucleotides to a template. that reads the original DNA strand and builds a complementary new strand using base pairingThe specific hydrogen bonding between complementary bases (A-T, C-G in DNA). rules. When everything works correctly, you get two identical copies of chromosome 7, each with a perfect CFTR gene. But sometimes—rarely, but sometimes—DNA polymerase makes a mistake. It might insert the wrong nucleotideThe basic building block of DNA and RNA, consisting of a sugar, phosphate group, and nitrogenous b, or skip one entirely, or add an extra one. These mistakes are called mutations, and they’re exactly how CF started in the first place. Someone’s ancestor, generations ago, had a DNA replication error in the CFTR gene, and that mutationA change in DNA sequence that can affect gene function. has been faithfully copied and passed down through families ever since. Today we’re going to understand how DNA replication usually prevents these disasters, and what happens on the rare occasions when it fails.
Key Concepts:
- DNA Replication Ensures Genetic Continuity – Before any cell divides, it must duplicate all 46 chromosomes so each daughter cell gets a complete set of genetic instructions, including the CFTR gene
- Semi-Conservative Replication – Each new DNA molecule contains one original strand and one newly synthesized strand, ensuring accurate copying through baseA substance that accepts hydrogen ions (H⁺) or releases hydroxide ions (OH⁻). pairing
- Replication Errors Create Mutations – When DNA polymerase makes mistakes copying the CFTR gene, the result is a mutation that may cause cystic fibrosis if passed to offspring
Pre Class Lectures
- DNA Structure 12 minutes
- DNA Replication 9 minutes
- The Cell Cycle 15 minutes
Post Class Lectures
- DNA to RNA 14 minutes
Lesson 3: The Cell Cycle & Mitosis – Distributing CFTR Genes
Let’s talk about the most elegant choreography in biology: mitosis. Your cells are constantly dividing to replace damaged ones (remember when you burned your mouthThe opening of the digestive tract where food enters and mastication begins. on hot pizza?), and every single time they divide, they have to perfectly distribute 46 chromosomes—including chromosome 7 with your CFTR gene—into two daughter cells. It’s like a molecular custody battle, except both kids get EVERYTHING. And when it goes wrong? Well, that’s how you get cells with too many chromosomes, too few chromosomes, or that wonderful thing we call cancer. No pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange., cellular machinery!
The respiratory epithelial cells lining your airways are some of the hardest-working cells in your body when it comes to division. They’re constantly exposed to dust, pollution, and irritants, so they need to be replaced regularly through mitosis. Every time one of these cells divides, it goes through a carefully orchestrated series of steps: the chromosomes condense, line up in the middle of the cell, get pulled apart to opposite ends, and finally separate into two new cells. Each daughter cell receives exactly 23 pairs of chromosomes, including one copy of chromosome 7 with the CFTR gene. Those daughter cells will then use their CFTR genes to make CFTR proteins, continuing the cycle. But here’s what makes mitosis so critical for CF patients: if you have a mutated CFTR gene, every single new cell produced through mitosis will also have that mutated gene. That’s why CF affects so many tissues—the mutation gets copied and distributed to every cell in the body.
Key Concepts:
- The Cell Cycle Prepares Cells for Division – During interphaseThe phase of the cell cycle in which the cell grows, performs its functions, and replicates DNA. (G1, S, G2 phases), cells grow, replicate their DNA including the CFTR gene, and prepare all cellular components for division
- Mitosis Distributes Chromosomes Equally – The phases of mitosis (prophaseThe first stage of mitosis where chromatin condenses into visible chromosomes., metaphaseA stage of mitosis where chromosomes align at the metaphase plate., anaphaseA stage in mitosis or meiosis where sister chromatids or homologous chromosomes separate., telophaseThe final stage of mitosis where nuclear envelopes reform around separated chromosomes.) ensure each daughter cell receives exactly one copy of each chromosome, including chromosome 7 with the CFTR gene
- Checkpoints Prevent Disasters – The cell has quality control mechanisms that detect errors in chromosome alignment or DNA damage and trigger cell death (apoptosisProgrammed cell death, an essential process for growth and development.) if problems can’t be fixed
Pre Class Lectures
- Mitosis 15 minutes
- The Cell Cycle 15 minutes
Post Class Lectures
- DNA Replication 9 minutes
- DNA Structure 12 minutes
Lesson 4: Putting It All Together – The CFTR Life Cycle
We’ve journeyed from DNA structure to protein synthesis to cell division. Now it’s time for the big reveal: how does a single fertilized egg with one copy of the CFTR gene from each parent turn into YOU, with trillions of cells all making CFTR protein? We’re going to trace the complete life cycle: from your parents passing down CFTR genes, to those genes being replicated billions of times, to those genes being transcribed and translated in every respiratory epithelial cell you make. This is the grand finale where molecular biology becomes human biology.
Here’s the complete story: You inherited two copies of chromosome 7—one from your biological mother and one from your biological father. Each chromosome 7 carries a CFTR gene. If you don’t have CF, both of those genes contain the correct sequence to make functional CFTR protein. From the moment you were conceived as a single fertilized egg, your cells have been going through this cycle over and over: (1) DNA replication copies your CFTR genes, (2) mitosis distributes those copies to daughter cells, (3) those daughter cells use transcription and translationThe process of converting mRNA into a protein. to make CFTR proteins, (4) the cells eventually divide again, and the cycle repeats. This process has happened trillions of times to build your body. But if someone has CF, they inherited two mutated CFTR genes, and that mutation gets faithfully copied and distributed to every cell through DNA replication and mitosis. That’s why gene therapy is so challenging—you can’t just fix one cell’s CFTR gene; you’d need to fix it in billions of cells across multiple tissues. Today we’re going to see how all these processes work together as an integrated system that maintains genetic information across your entire lifetime.
Key Concepts:
- Inheritance → Replication → Division → Protein Synthesis Forms an Integrated Cycle – The CFTR genes you inherited get replicated before every cell division, distributed to daughter cells through mitosis, and then used to make proteins through transcription and translation
- CF is a Genetic Disease Because Mutations Are Copied and Distributed – A mutated CFTR gene gets replicated with the same fidelity as a normal gene, meaning every cell descended from the fertilized egg will carry that same mutation
- Understanding the Cycle Explains Why Treatment is Complex – Since the mutated CFTR gene exists in trillions of cells throughout the body, any genetic treatment would need to reach and correct the gene in vast numbers of cells across multiple tissue types
MiniLectures
DNA Structure
12 Minutes
Inside every single cell of your body is a molecule so long that if you stretched it out, it would measure about 2 meters—yet it’s packed into a nucleus so small you can’t even see it without a microscope. That molecule is DNA, and it contains the complete instruction manual for building and operating YOU. The elegance of DNA’s double helixThe twisted-ladder structure of DNA molecules. structure isn’t just beautiful—it’s functional. Those two strands wind around each other like a twisted ladder, with the rungs made of complementary base pairs (A with T, G with C) that can separate and come back together like the world’s most perfect zipper. The sequence of those four simple letters—A, T, G, C—is sophisticated enough to encode everything from your eye color to whether you can make functional CFTR protein.
DNA Replication
10 Minutes
Your body is currently performing one of the most impressive copying jobs in the known universe, and you’re not even aware of it. Right now, billions of your cells are duplicating their entire genetic instruction manual—all 3 billion base pairs—with an error rate of about 1 mistake per 10 billion nucleotides. That’s like copying the entire Encyclopedia Britannica a thousand times and making one typo. Of course, when that ONE typo happens to be in an important gene like CFTR, you get cystic fibrosis, so the stakes are fairly high. No pressure, DNA polymerase. We’re going to watch this molecular copy machine in action and understand why your cells spend so much energyThe capacity to do work or cause change. making sure the recipe for you gets passed along accurately to every daughter cell. Sometimes they mess up anyway, and that’s how mutations happen.
DNA to RNA
14 Minutes
Your DNA is like a master recipe book that never leaves the kitchen safe—it’s too valuable to risk damage. So when your cells need to make a protein, they don’t use the original instructions directly. Instead, they make a quick disposable photocopy called messenger RNA (mRNA) that can travel out to where the work actually happens. This copying process is called transcription, and it’s happening thousands of times per second in every cell of your body right now. But here’s what makes it fascinating: your cells don’t transcribe the entire genomeThe complete set of genetic material in an organism. all at once. They’re incredibly selective, only making mRNA copies of the genes they actually need in that moment. A respiratory epithelial cell transcribes the CFTR gene constantly because it needs that protein, while a neuron never bothers—same DNA, different choices.
The Cell Cycle
15 Minutes
Welcome to the most bureaucratic process in biology: the cell cycleThe sequence of events in a cell’s life, including growth, DNA replication, and division., where cells spend most of their time NOT dividing but instead filling out paperwork and waiting at checkpoints. Your cells have a life cycle just like humans do (infant, adolescent, adult), except instead of growing up and retiring, they grow, copy all their homework, grow some more, maybe pass a few quality control inspections, and then—if they’re lucky and haven’t been flagged for apoptosis—they split into two clones of themselves. The whole process is about as exciting as waiting at the DMV, except when the checkpoints fail and you get cancer, which is decidedly less boring and significantly more deadly. Today we’re going to walk through the thrilling stages of G1 (growthAn increase in size and number of cells.), S (copying DNA while hoping not to mess up), G2 (more growth and panic-checking that everything copied correctly), and M (the actual division part that everyone thinks is the whole story). Spoiler alert: most of a cell’s life is spent in the gap phases doing prep work, which is probably a metaphor for something.
RNA to Protein
17 Minutes
The ribosome is perhaps the most remarkable molecular machine you’ve never heard of. This two-part structure reads a string of nucleotides (your mRNA) and somehow translates that sequence into a completely different language—amino acids—to build proteins. Think about what that means: a sequence of As, Us, Gs, and Cs gets decoded three letters at a time, and each three-letter “word” (codon) specifies exactly which amino acidThe building blocks of proteins, consisting of an amino group, carboxyl group, and side chain. should come next. It’s like having a decoder ring that translates Morse code directly into architecture, building complex functional structures one piece at a time. And the ribosome does this at a rate of about 15-20 amino acids per second, with helper moleculesGroups of atoms bonded together. called tRNA bringing in the right amino acidA substance that releases hydrogen ions (H⁺) in solution. for each codon. By the end of this lecture, you’ll understand how a gene sequence like the one for CFTR gets translated into a 1,480-amino-acid-long protein chain—and why getting even one amino acid wrong can cause the entire protein to fail. This is where the genetic codeThe set of rules by which DNA sequences are translated into proteins. becomes physical reality.
Mitosis
14 Minutes
If you’ve ever watched a carefully choreographed dance performance where one misstep would cause the entire production to collapse, you’ll appreciate mitosis. This is the process where a cell takes 46 duplicated chromosomes and distributes them perfectly into two daughter cells—each getting exactly 23 pairs, no more, no less. The chromosomes line up in the middle of the cell during metaphase like dancers waiting for their cue, then get pulled apart to opposite ends during anaphase by molecular ropes called spindle fibers. It’s precise, it’s elegant, and it absolutely HAS to work correctly because if even one chromosome ends up in the wrong place, the resulting cells won’t be identical clones. One might have two copies of chromosome 7 (with CFTR), and the other might have none. Today you’re going to learn the four phases of mitosis—prophase, metaphase, anaphase, and telophase—and understand why this process is essential for growth, repair, and replacing damaged cells. And yes, we’re going to talk about what happens when mitosis goes wrong, because that’s how you get tumors.
Cystic Fibrosis
Minutes
Cystic fibrosis is a disease caused by a protein that doesn’t work—or doesn’t exist at all—in the cells lining your airways. That protein is called CFTR (cystic fibrosis transmembrane conductance regulator), and its job is deceptively simple: move chloride ionsCharged atoms or molecules. from inside the cell to outside the cell. But when CFTR fails, chloride gets stuck inside, and water—being the clingy molecule it is—follows the chloride and stays inside too. The result? Thick, sticky mucus that can’t be cleared from the lungs, leading to chronic infections and progressive lung damage. What makes CF particularly interesting from a molecular biology perspective is that there are over 2,000 different mutations in the CFTR gene, each causing the protein to fail in slightly different ways. Some mutations mean the protein never gets made. Others mean it gets made but folds wrong. Still others mean it gets made correctly but ends up in the wrong place in the cell membrane. Today we’re going to explore the most common mutation (ΔF508), understand why one missing amino acid causes such catastrophic problems, and see how this connects to everything you’ve learned about DNA, protein synthesis, and cellular function. This is where molecular biology meets real human disease.
By the End of this Module You Will be Able to:
- Explain the stages of transcription and translation
- Describe how genetic information flows from DNA to RNA to protein (Central Dogma)
- Identify the roles of mRNA, tRNA, ribosomes, and the genetic code in protein synthesis
- Analyze how mutations in DNA sequences result in altered proteins
- Describe the process of DNA replication and explain its necessity before cell division
- Explain when DNA replication occurs during interphase (specifically S phaseThe DNA synthesis phase of the cell cycle where chromosomes are replicated.)
- Analyze how replication errors lead to mutations and their consequences
- Connect DNA replication to the inheritance of genetic diseases like cystic fibrosis
- Describe the stages of the cell life cycle, including mitosis, interphase, and cytokinesis, and explain their significance
- Discuss the regulation of the cell life cycle (checkpoints at G1, G2, and metaphase)
- Discuss the relationship between cell division and cancer
- Explain how mitosis ensures each daughter cell receives identical genetic information
- Define differentiation and explain how cells with identical DNA can become specialized
- Integrate the processes of DNA replication, mitosis, transcription, and translation to explain genetic continuity
- Explain the complete cell cycle including when DNA replication, protein synthesis, and division occur
- Define differentiation and explain its importance in how cells with identical DNA become specialized
- Evaluate why genetic diseases affect all cells that need to express a particular gene
- Analyze the challenges of gene therapy as a treatment for genetic diseases
List of terms
- cells
- proteins
- nucleotides
- nucleus
- ribosomes
- DNA polymerase
- base pairing
- nucleotide
- mutation
- base
- mouth
- pressure
- interphase
- prophase
- metaphase
- anaphase
- telophase
- apoptosis
- translation
- anatomy
- double helix
- energy
- genome
- cell cycle
- growth
- amino acid
- molecules
- acid
- genetic code
- ions
- S phase