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Chapter 13

Chapter 13. RNA & Protein Synthesis. Gene Expression. When a cell “reads” the DNA, it doesn’t directly say for example blue eyes. What the DNA actually says is what types of proteins to make, when to make them, & how much of them to make. This is what we term gene expression .

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Chapter 13

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  1. Chapter 13 RNA & Protein Synthesis

  2. Gene Expression • When a cell “reads” the DNA, it doesn’t directly say for example blue eyes. • What the DNA actually says is what types of proteins to make, when to make them, & how much of them to make. • This is what we term gene expression. • Expressing the genetic information by using the DNA code to create a protein that does a specific job or controls a specific trait.

  3. Gene • Not all your DNA actually codes for something. • Some of your DNA is junk DNA. • Scientists are still not sure what all of your DNA does. • However, a gene is a specific segment of DNA that does code for something. •  It codes for a protein! • Each chromosome contains many genes  controls many proteins - traits

  4. What is a protein? • Made up of the elements: C, H, O, N • Chain of amino acids – polypeptide • Function as enzymes (control reactions), messengers, structural components (muscles) • About 20 different amino acids (differ by their r/variable group) • The particular sequence or pattern of amino acids in the chain makes one protein different from another.

  5. Protein Structure

  6. DNA to a protein • The sequence or pattern of these amino acids that make up a protein are coded for in your DNA. • This is one of the ways that you DNA is the instructions that make you = you. • But what happens if there is a change or mutation to the DNA? • If the DNA gets change then you do not make the right protein, which means whatever job that protein was suppose to do doesn’t get done. • Many genetic disorders are due to such mutations.

  7. Overall Order • DNA  mRNA  Protein

  8. Protein Synthesis • 2 stages • Transcription Translation • (nucleus) (ribosome) • Convert DNA into mRNA Convert mRNA into a protein

  9. DNA vs. RNA DNA RNA Single Stranded Can leave the nucleus (pores) A U C G Sugar – Ribose 3 Types • Double Stranded • Does not leave the nucleus • A T C G • Sugar - Deoxyribose

  10. Types of RNA • mRNA – messenger RNA • carries the message of how to make a protein from the nucleus to the ribosome • determines the order of amino acids in a protein • contains the codon (group of 3 “letters” on the mRNA) • rRNA – ribosomal RNA (makes up the ribosome) • tRNA – transfer RNA • carries or transports the amino acids needed to make the protine to the ribosome • contains the anticodon

  11. Transcription • Purpose: convert DNA into mRNA • Location: Nucleus • 3 Steps: • Initiation • Elongation • Termination • Enzyme: RNA Polymerase

  12. Practicing Transcription • Let’s say this is our DNA  TACATTCGGATC • What would our mRNA look like? • Use the rules of base pairing! • Except now A – U, C – G

  13. Practicing Transcription • DNA  TACATTCGGATC • mRNA  AUGUAAGCCUAG

  14. Translation • Purpose: convert mRNA into a protein • Location: Ribosome • 3 Steps: • Initiation • Begins when the ribosome reaches the start codon (3 letters on mRNA usually AUG) • Elongation • Protein gets bigger by adding more amino acids. • Termination • Ribosome reaches a stop codon. (UAA, UAG, or UGA)

  15. Translation – Draw A picture!

  16. Translation

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