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Cambridge Pre-U Biology - 1.6 Genes and Protein Synthesis PART 1 Sample

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This is a widescreen fully animated and editable PowerPoint presentation that covers the first half of section 1.6 of the Cambridge Pre-U Biology course.

It is 64 slides long and covers the following topics:

What is a gene?
How does the genetic code work?
Protein synthesis
The lac operon
Variation
Proteomics and genomics

The full PowerPoint can be downloaded from mrexham.com

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Cambridge Pre-U Biology - 1.6 Genes and Protein Synthesis PART 1 Sample

  1. 1. MAKING SENSE OF Icons CC – The Pink Group Copyright©2017HenryExham
  2. 2. Copyright © 2017 Henry Exham • This is it! This is how the whole thing works! • You now have enough biology knowledge to understand how all the pieces of the puzzle go together to build living organisms. • In this topic you will learn how the genetic code works to make polypeptides and RNA which go onto give cells their structure and function and therefore build organisms. • You will learn the details of exactly how this works and how these instructions are inherited by the next generation. • Finally you will learn about what can go wrong! 2
  3. 3. MAKING SENSE OFMAKING SENSE OF Gene expression Variation Inheritance 3 Mutations The genetic code and protein synthesis PART1PART2
  4. 4. Copyright © 2017 Henry Exham a) Define a gene as a unit of inheritance or as an ordered sequence of nucleotides located at a particular locus on a particular chromosome, which codes for a particular protein or, in certain cases, a functional or structural RNA molecule and discuss the limitations of these definitions with reference to introns, exons and promoters. b) Describe the genetic code and discuss the extent to which it is true that the code is universal to all organisms. c) Explain protein synthesis in terms of transcription and translation, including the roles of DNA, mRNA, tRNA and ribosomes. d) Describe, in outline, eukaryotic introns, exons and the splicing of mRNA. 4
  5. 5. Copyright © 2017 Henry Exham • By now you should know what DNA looks like and how it divides but we still haven't covered how it actually works! 5
  6. 6. Copyright © 2017 Henry Exham • The sequence of bases in DNA is actually a code to make proteins. • We have already explained how important proteins are to living organisms. • Machinery in cells can read this code and manufacture the proteins (protein synthesis). • Every three bases on the DNA codes for an amino acid. • This is called the triplet code. 6
  7. 7. Copyright © 2017 Henry Exham • There are 64 combinations of bases (43) for only 20 amino acids, so amino acids are usually coded for by more than one triplet code. • For example the codes TGA, TGG, TGT and TGC all code for the amino acid threonine. • This is known as a degenerate code, but its good because it means that often mutations in the DNA don’t actually change the eventual protein produced so it protects the organism. • Most of your DNA actually doesn't’t code for proteins but it regulates when and where to make them. 7
  8. 8. Copyright © 2017 Henry Exham • The triplet code works the same in all living organisms (with a couple of exceptions). • Therefore it’s (almost) universal. • That means we can swap DNA between organisms! • This is explained later in the course. 8
  9. 9. Copyright © 2017 Henry Exham • As mentioned there are a couple of exceptions to the genetic code being universal. • The majority of these exceptions are found in the DNA inside the mitochondria (mtDNA) which code for different amino acids than the nuclear DNA. 9By Jfitz1974 - Using Adobe Photoshop Elements, CC BY-SA 3.0, https://en.wikipedia.org/w/index.php?curid=41045504 Recently some modifications have also been discovered in the nuclear DNA of some species.
  10. 10. Copyright © 2017 Henry Exham 10 So what exactly is a gene?
  11. 11. Copyright © 2017 Henry Exham • You probably know this definition: 11 A gene is a section of DNA that codes for a particular protein. However, at this level we can go into this definition further and actually see why this is not a good definition at all.
  12. 12. Copyright © 2017 Henry Exham • You probably know this definition: 12 A gene is a section of DNA that codes for a particular protein. By OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30148169 But what about proteins with quaternary structure like this one? Are they coded for by one gene?
  13. 13. Copyright © 2017 Henry Exham • You probably know this definition: 13 A gene is a section of DNA that codes for a particular protein. By OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30148169 No they are not, they are made of multiple polypeptides coded for by separate genes and then modified by the Golgi apparatus. A gene is a section of DNA that codes for a particular polypeptide. Therefore . . .
  14. 14. Copyright © 2017 Henry Exham • But in actual fact genes don’t always code for polypeptides, they can also code in certain cases for a functional or structural RNA molecule. 14 A gene is a section of DNA that codes for a particular polypeptide. By Yikrazuul - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10242870 Large ribosomal subunit (50S) of Haloarcula marismortui. The ribosomal proteins are shown in blue, the rRNA in ochre.
  15. 15. Copyright © 2017 Henry Exham • Another problem with this definition is that it is not one discrete section of DNA that makes up the actual gene. Its more complicated than that! • A better definition of a gene’s structure is to say an ordered sequence of nucleotides located at a particular locus (plural loci) on a particular chromosome. 15 A gene is a section of DNA that codes for a particular polypeptide or in some cases an RNA molecule.
  16. 16. Copyright © 2017 Henry Exham • But genes are not all at one locus! They are actually interrupted by non-coding sequences called introns. And begin with sections called promoters. • The coding sequences in the gene are called exons. 16 A gene is a section of DNA that codes for a particular polypeptide or in some cases an RNA molecule.
  17. 17. Copyright © 2017 Henry Exham To download the whole presentation visit www.MrExham.com
  18. 18. This PowerPoint is protected under copyright. It is designed for educational use. Either personal study or to be presented to a class. It may be edited or duplicated for these purposes only. It must not be shared or distributed online in any format. Some images used are under a separate creative commons license, these are clearly marked. Copyright © 2017 Henry Exham Brought to you by MrExham.com

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