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Looking for a summary of the Hershey-Chase experiments? Let's go! Is protein or DNA the genetic material? To find out, Hershey and Chase used E. coli bacteria and the T2 bacteriophage. Key steps in the experiments included: * 02:12 Using *radioactive isotopes* to label bacteriophage DNA and bacteriophage protein. - Phages were cultured in medium containing EITHER sulfur-35 (35S) or phosphorus-32 (32P) - Protein was labeled with Sulfur-35 (sulfur is present in protein but not DNA) - DNA was labeled with Phosphorus-32 (phosphorus is present in DNA but not protein*) * 03:58 *Infecting E. coli* with labeled phages - one batch of bacteria was infected with 35S phages (labeled protein), one batch was infected with 32P phages (labeled DNA) * 04:46 Using a *blender* to shake off the phage ghosts from the infected bacteria * 05:32 Using *centrifugation* to separate the bacteria from the rest of the mix (forming a pellet of bacterial cells) * 06:27 *Detecting radiation* - In the batch with 35S phages, radioactivity was found in the supernatant, indicating that phage proteins did NOT enter the bacterial cells during infection - In the batch with 32P phages, radioactivity was found in the pellet, indicating that phages pass their DNA to bacteria during infection *Conclusion: DNA, not protein, is the genetic material!* This added even more evidence showing that DNA is the molecule of inheritance! Check out the Avery, Macleod, McCarty experiments for even more… *Quick note about proteins and phosphorus – none of the 20 amino acids contain phosphorus, but after a protein is assembled, it can get some additional modifications to help it function or to make it active/inactive. Some proteins will have phosphorus added as part of this process – you may run into phosphorylation in your studies, so don’t panic if you see phosphorus in proteins later on :) Luckily, that wasn’t a problem for this study! Connect with me! *Website:* http://www.yourotherbioprof.com *Instagram:* instagram.com/yourotherbioprof

If you're studying #mitosis or #meiosis, you're going to run into chromatids - but don't let them stress you out! From the time the DNA replicates [S phase] until the sister chromatids are separated [anaphase of mitosis or anaphase II of mitosis], the 2 chromatids make up our replicated, x-shaped chromosomes. Once the two chromatids are pulled apart, they're now independent chromosomes! MORE INFO: Replicated chromosomes: https://youtu.be/cPAMTwl6e08?si=3GXTXfWYXxif-f9I DNA Replication: https://youtu.be/l_QKFdin6uk?si=PDjZmj5p7GLe34L4

#POLYPLOIDY is extra sets of chromosomes - more than two. We can describe polyploids based on WHERE those extra chromosomes came from - are they from the same species, or another one? In #AUTOPOLYPLOIDY (or "self" polyploidy), those chromosomes come from the *same species.* So we could have a plant that has a little bit of trouble in meiosis and creates diploid [unreduced] gametes. Those gametes self-fertilize creating an AUTOTETRAPLOID: four sets of chromosomes, all from the same species - in this case, the same individual! #ALLOPOLYPLOIDY ("other" polyploidy) means that the extra chromosomes are coming from *different species.* Now this can get a little bit trickier because hybrids tend to be sterile - the chromosomes from "Species A" and from "Species B" don't pair up during meiosis. But with a little extra step - like a whole genome duplication - we can restore homologous chromosomes and get an ALLOTETRAPLOID, four sets of chromosomes from different species! These are just two examples - there are even more ways to generate polyploids!

DNA and RNA have a lot in common, but also some pretty important differences - let's check those out! In this video, we'll compare DNA and RNA in terms of their functions, locations in the cell, lifespans, and structures (lengths, subunits, molecular structure, and base-pairing). [IB Bio A1.2.7] 00:00 Intro 00:27 FUNCTIONS of DNA and RNA are different 01:36 LOCATIONS of DNA and RNA in a cell 02:48 LIFESPAN of DNA and RNA molecules 03:04 DNA and RNA NUCLEOTIDES 03:59 SUGARS [deoxyribose in DNA and ribose in RNA] and the 2' carbon 05:03 NITROGENOUS BASES [purines and pyrimidines] 05:56 THYMINE in DNA, URACIL in RNA 06:35 SECONDARY STRUCTURES of DNA and RNA [double helix, hairpins] 08:03 LENGTH [spoiler: DNA is longer!] 08:20 BASE-PAIRING: complementary bases pair up (G-C, A-T in DNA; G-C, A-U in RNA) 10:16 More comparisons? 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 References and more info: Human RNA lengths: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5199132/ Human chromosome lengths: https://www.ncbi.nlm.nih.gov/grc/human/data

Are you asking yourself, "how does base-pairing wobble during translation?" I got you! "Wobble" is all about how the codon-anticodon pairing rules get extra-flexible at one particular base. This allows for an anticodon to bind with multiple codons for the same amino acid, so the cell doesn't have to make as many different types of tRNAs. At the wobble site, we can have... 1. Normal base-pairing (A-U, G-C) 2. G-U pairing 3. Inosine in the anticodon pairing with A, C, or U in the codon 00:00 Intro 00:25 Codon table 01:36 Stop codons bind release factors, not anticodons! 01:59 Why don't we need 61 different types of tRNAs for 61 different codons? 03:02 Redundancy of the genetic code; synonymous codons 05:15 The wobble position 06:21 Expanded base-pairing rules at the wobble position 08:07 Inosine in the anticodon pairs with A, C, or U in the codon 09:54 Codon usage bias 11:04 Some anticodons aren't produced 14:07 Review *NOTES* You'll often see the word "degenerate" used to describe how a single amino acid can be encoded by more than one codon - same idea as "redundant" here. :) "Inosine" is actually the name of the nucleoside that contains our modified base AND a pentose sugar (like how an adenine base and a pentose sugar = the nucleoside "adenosine"). The name of the base in inosine is "hypoxanthine," but unless your class has a heavy biochemistry component, you're not likely to find this referred to as anything but inosine in the context of wobble. *Connect with me!* Website: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof *References* Codon usage bias data found at: genscript.com/tools/codon-frequency-table

Wondering why DNA uses thymine (T), but RNA uses uracil (U)? Scientists have a few hypotheses as to why the nucleic acids switch up that base - we'll look at a couple here (more listed below)! We'll explore how the use of thymine vs. uracil might be a trade-off between saving energy and keeping the sequence stable: 00:00 Intro 00:25 The pyrimidines (cytosine, uracil, thymine) 01:17 Why not use thymine in both DNA and RNA? 02:07 Why not use uracil in both DNA and RNA? 02:27 Cytosine deaminates to uracil 03:46 Uracil methylation makes thymine 04:46 Recap! 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 *MORE ideas about Thymine vs Uracil!* - Uracil is less-specific with base-pairing (doesn't ONLY pair with A! Example: "wobble" in translation): https://doi.org/10.1093/embo-reports/kvd001 wobble video coming soon! - Methylation may protect DNA from enzymatic attack: https://doi.org/10.1093/nar/9.22.5859 *Read more:* Nice description of early DNA (from uracil-DNA to thymine-DNA): https://www.ncbi.nlm.nih.gov/books/NBK6360/

Ready to label DNA Structure? In this video, we'll cover the key structures that make up a DNA molecule, so that you can recognize the parts and understand the terms. We'll label: Nucleotides Pentose sugar [deoxyribose] Phosphate group Nitrogenous base [Purine and Pyrimidine] 5' and 3' ends Hydrogen bonds Phosphodiester bonds ...and explain what it means to be Complementary and Antiparallel. http://www.yourotherbioprof.com 00:00 Intro 00:15 3 Parts of a Nucleotide [Sugar, Phosphate, Base] 00:48 Purine vs. Pyrimidine - how to remember? [Nitrogenous Bases] 01:37 5 Nitrogenous bases 01:47 Double Helix 02:17 Complementary Bases and Hydrogen Bonds 03:22 DNA is antiparallel (5' and 3' ends) 04:29 Phosphodiester bonds 05:15 Sugar-phosphate backbone 05:48 Recap! 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

Looking for tips on how to label a DNA replication fork? In this video, we'll walk through labeling two common types of replication fork diagrams you may encounter on homework or an exam. Along the way, I'll give you some tips on what to look for so that you can label your own! We'll label: 5' and 3' ends DNA template strands Leading and lagging strands Okazaki Fragments RNA Primers ...and a bunch of proteins, including: Single-Strand Binding Proteins, Helicase, Gyrase (Topoisomerase), DNA Polymerase III, DNA Polymerase I, Primase and Ligase! 00:00 Intro 00:17 TWO COMMON TYPES OF REPLICATION FORKS 00:34 REPLICATION BUBBLES AND REPLICATION FORKS 01:34 LABEL A REPLICATION FORK 04:39 LABEL A REPLICATION FORK WITH PROTEINS [PROKARYOTIC] 09:21 Wrap-up New videos are always on the way - subscribe so you don't miss any of my biology tips :) Connect with me! Tutoring information: http://www.yourotherbioprof.com Instagram: instagram.com/yourotherbioprof