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Why is the trp operon negative repressible? How does attenuation stop transcription of the trp operon? How do bacteria turn genes off? The tryptophan operon ("trp operon") in E. coli has two key regulatory mechanisms - let's look at both! The trp operon is regulated by a *negative repressible* mechanism, and by *attenuation,* where translation (the position of the ribosome) actually impacts transcription! *When tryptophan concentration in the cell is low*, the cell wants to keep transcription of the trp operon ON - to make the instructions to build more enzymes to make more tryptophan. The trp repressor stays out of the way, allowing RNA polymerase to start transcription. Translation of that mRNA starts, too! The low trp levels mean tRNAs charged with tryptophan are hard to find, so the ribosome stalls, waiting for a tryptophan delivery. An *antitermination hairpin* forms, and RNA polymerase keeps moving along... *When tryptophan concentration in the cell is high*, the trp repressor binds excess tryptophan, causing a conformational change in the trp repressor. This allows the repressor to *bind the operator - blocking RNA polymerase* from initiating transcription. But the repressor isn't perfect - it can fall off the operator prematurely, allowing transcription to begin (even though it's not needed). Thanks to plenty of trp-charged tRNAs, the ribosome moves quickly, causing formation of a *termination hairpin*, and stopping this unneeded transcription. #repressor #attenuation #trpoperon *Operons: Positive, Negative, Inducible, Repressible:* https://youtu.be/Qd16nt1WdAc *What does Upstream Mean on DNA and RNA?:* https://youtu.be/XDKUL9JB66s 00:32 Structure of the trp operon 01:40 Trp operon with low tryptophan concentration 02:39 Trp operon with high concentration of tryptophan 03:18 The trp operon is a negative repressible operon 04:01 Trp leader region (trpL) and hairpins 05:09 Transcription and translation happen in the same place in prokaryotes 05:39 trpL mRNA has tryptophan codons 05:58 Attenuation of transcription (termination hairpin) 06:49 Antitermination hairpin with low trp concentration 07:32 Summary of attenuation trp operon 08:20 Attenuation of operons that produce amino acids 08:45 Why attenuation of trp operon? 09:16 Summary of trp operon regulation New videos are always on the way - subscribe so you don't miss any of my biology tips :) Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof

A quick explanation of negative inducible operons. Key vocabulary: negative regulation, repressor, operator, inducible, inducer New videos are always on the way - subscribe so you don't miss any of my biology tips :) Ready to learn more? *Positive, Negative, Inducible, Repressible Operons:* https://youtu.be/Qd16nt1WdAc Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof

Upstream and downstream tell us about directions of features on DNA and RNA - in your biology textbook, you'll probably see the phrase "the promoter is upstream of the gene," but what does that actually mean? In this video, we'll see what it means for something to be upstream or downstream of something else on DNA or RNA. And we'll see how directionality (5' and 3') can show you which way is upstream, and where the promoter should be. #DNA #RNA #upstream 00:14: Upstream and Downstream on RNA 01:22: Upstream and Downstream of a Gene (DNA) 02:30: The Promoter is Upstream of the Gene New videos are always on the way - subscribe so you don't miss any of my biology tips :) Ready to learn more? Check out these related videos: *5' and 3' (Antiparallel)*: https://youtu.be/cJtuW1yXQ7E *Transcription Bubble*: https://youtu.be/ddsJf3CkDKk *Coding and Template Strands*: https://youtu.be/T0ZQUx8TmtQ Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof

What is the difference between genotype and phenotype? In this quick video, we'll review genotype and phenotype - with examples! - and see that both genotype and the environment can shape a phenotype. #genotype #phenotype #alleles 00:12: What is a phenotype? Give an example of a phenotype. 00:45: What is a genotype? Give an example of a genotype. 01:02: What are alleles? 01:30: Homozygous and heterozygous genotypes 02:07: Genotype and environment impact phenotype Learn more! Homologous Chromosomes: https://youtu.be/DK-lLhqNd0c Dominant and Recessive Alleles: https://youtu.be/7DmaUO-BNFM Haploid, Diploid, Triploid: https://youtu.be/L3_epMYckvo Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof

What are Chargaff's rules? How were Chargaff's rules created? And how can you solve problems with Chargaff's rules? Let's work that out! In this video, we'll review nucleotides and nitrogenous bases and give a little historical context. We'll summarize Chargaff's experiment that produced his "rules," and how that led to the falsification of the tetranucleotide theory. We'll work practice problems (just a little math), and point out common student errors to avoid so that you can get all those points on your exam! #chargaffsrules #nucleotides #tetranucleotidetheory New videos are always on the way - subscribe so you don't miss any of my biology tips :) *What's in this video:* 00:21 Review: nucleotides and nitrogenous bases (adenine, cytosine, guanine, thymine) 01:17 Review: tetranucleotide hypothesis 01:53 Review: Chargaff's experiment 02:36 A = T and G = C 03:01 DNA base composition varies between species 03:22 Practice problems with Chargaff's Rules 05:14 Exceptions to Chargaff's Rule Learn more about DNA and its history: DNA Structure: https://youtu.be/naOaTy30cgs Compare DNA and RNA: https://youtu.be/eXHfQLEnJEY Hershey Chase Experiment: https://youtu.be/Q03WhnAWoqI Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof AP Biology Unit 1.5 IB Biology A1.2.15

How do you label a transcription bubble diagram? Which strand is the coding strand? Not sure where to stick all of the 5' and 3' ends on your transcription bubble? Wondering how to find the direction of transcription? Let's do it! In this video, we'll review... *01:06 Transcription bubble and summary of transcription initiation, elongation *02:08 Template DNA and Nontemplate DNA strands *02:27 Labeling 5' and 3' ends of RNA (in a transcription bubble) *03:05 Direction of transcription *03:41 Complementary base pairing of DNA and RNA *04:15 Labeling 5' and 3' ends of DNA (in a transcription bubble) *04:39 Sense and coding strands ...and we'll finish with a little practice! RELATED VIDEOS! *DNA Replication Fork:* https://youtu.be/l_QKFdin6uk *More about 5' and 3' Ends:* https://youtu.be/cJtuW1yXQ7E *Why Thymine and Uracil?* https://youtu.be/o9jj7C0_H9U *Coding, noncoding, sense, antisense...* https://youtu.be/T0ZQUx8TmtQ New videos are always on the way - subscribe so you don't miss any of my biology tips :) Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof #transcription #transcriptionbubble #biology

Regulation of operons can be positive, negative, inducible, repressible - what does it mean?! And what makes an operon positive inducible, negative inducible, positive repressible or negative repressible? It’s all about controlling transcription! In this video, we’ll: * 01:05 Compare *positive* and *negative* control of transcription * 02:21 Compare *inducible* and *repressible* operons * 05:02 Explain operon *regulatory protein* conformations (activators vs. repressors) And finally, walk through diagrams of each operon category: * 06:38 *negative inducible operon* * 07:49 *negative repressible operon* * 08:41 *positive inducible operon* * 09:25 *positive repressible operon* New videos are always on the way - subscribe so you don't miss any of my biology tips :) Connect with me! Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof #inducibleoperon #repressibleoperon #generegulation #operon

The differences between haploid (n), diploid (2n), and triploid (3n)...but with candy! In this short, we'll (quickly!) identify: * a haploid cell * the haploid number (n) * a diploid cell (and what 2n means) * a triploid cell (and what 3n means) * homologous chromosomes * why chromosomes might be different colors in a drawing