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Unit 7

Unit 7. RNA, Protein Synthesis & Gene Expression Chapter 10-2, 10-3 ( page 190 – 197 ) Chapter 11 ( pg 203 – 214 ). Unit 7. Lecture 1 Topics: DNA vs RNA Covers: Chapter 10-2 Pages 190 - 191. RNA Introduction.

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Unit 7

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  1. Unit 7 RNA, ProteinSynthesis & Gene Expression Chapter10-2, 10-3 (page 190 – 197) Chapter11 (pg 203 – 214)

  2. Unit 7 • Lecture 1 • Topics: • DNA vs RNA • Covers: • Chapter 10-2 • Pages 190 - 191

  3. RNA Introduction • RNA (Ribonucleic Acid) is another type of nucleic acid. • Nucleic Acid – Organic compound, polymer made up of monomers known as nucleotides • RNA uses the genetic information stored in DNA to create proteins. Remember: • DNA stores genes and is kept in the nucleus • Gene – code for a protein • Ribosomes (outside nucleus) make proteins • Protein synthesis – process where a cell makes a protein

  4. Protein Review • Proteins are polymers made up of monomers known as amino acids • A chain of many amino acids is known as a polypeptide • Once a polypeptide is folded/coiled into its final shape, then it is called a protein • The shape (and function) of each protein is very different • A gene codes for the order of amino acids in a protein • The sequence of amino acids determines how the polypeptide will eventually coil/fold on itself (determines final shape of protein) • There are twenty different kinds of amino acids • Each amino acid is coded for by a specific combination of nucleotides

  5. Protein Review

  6. Comparison of DNA and RNA

  7. Comparison of Three types of RNA • rRNA (Ribosomal RNA) • Makes up part of a ribosome • Remember: • Ribosomes are made up of RNA and proteins • Ribosomes are organelles that make proteins

  8. Comparison of Three types of RNA • mRNA (Messenger RNA) • Brings the genetic message from DNA to a ribosome • DNA gene (protein message) copied into mRNA

  9. Comparison of Three types of RNA • tRNA (Transfer RNA) • Used during protein synthesis • Transfers amino acids to their proper place in the amino acid chain  

  10. END OF LECTURE 1

  11. Unit 7 • Lecture 2 • Topic: • Introduction to Protein Synthesis • Covers: • Chapter 10-2 and 10-3 • Pages 191 – 195

  12. Protein Synthesis • DNA (Chromosomes) store genetic information. Each strand of DNA stores hundreds of genes • The order (sequence) of nucleotides in the gene codes for the order of amino acids in the protein • A mutation that occurs in a gene could affect the protein code • Mutation – change in the order of nucleotides (DNA or RNA) • A gene mutation could change the order of amino acids in the protein or could prevent the protein from being made

  13. Protein Synthesis • To make a protein: 1. A copy of a gene is made (DNA copied into mRNA) • This mRNA template serves as the code for the protein, instructions for how to make the protein 2. mRNA carries the protein code from the nucleus to a ribosome • Protein synthesis takes place outside the nucleus by a: • Bound ribosome – makes proteins to leave the cell • Free ribosome – makes proteins to be used in the cell 3. Ribosome translates mRNA sequence into an amino acid sequence 4. The chain of amino acids will fold into final protein product

  14. Protein SynthesisThe Genetic Code • The order of nucleotides in the mRNA template codes for the order of amino acids in the protein chain • Ribosome translates the information from mRNA into amino acids • mRNA is made up of nucleotides; Proteins made up of amino acids

  15. Protein SynthesisThe Genetic Code • A combination of three nucleotides codes for one amino acid • CODON – Three nucleotide sequence that codes for an amino acid • 64 codons, but there are only 20 amino acids • Some amino acids have more than one codons • Important codons: START (AUG), and STOP (UAA, UAG, UGA)

  16. Phenylalanine (Phe), Leucine (Leu), Isoleucine (Ile), Methionine (Met), Valine(Val), Serine (Ser), Proline(Pro), Threonine (Thr), Alanine (Ala), Tyrosine (Tyr), Histidine(His), Glutamine (Gln), Asparagine (Asn), Lysine (Lys), Aspartic acid (Asp), Glutamic acid (Glu), Cysteine (Cys), Tryptophan (Trp), Arginine (Arg), Glycine (Gly)

  17. Protein SynthesisThe Genetic Code • Each amino acid is carried through the cell and to the ribosome by a specific tRNA(Transfer RNA) • tRNA is shaped like a “t” • One end (end of chain) bonds to a specific amino acid • Opposite end (bottom loop end) attaches to mRNA • This section is known as the ANTICODON • Anticodon is complementary to each mRNA codon • Example: Amino Acid – Serine • CODON – “AGU” • Serine transferred to amino acid chain by tRNA with the ANTICODON – UCA

  18. End of Lecture 2

  19. Unit 7 • Lecture 3 • Topic: • Protein Synthesis • Transcription • Translation • Covers: • Chapter 10-3 • Pages 193 – 196

  20. Protein Synthesis • Protein Synthesis is a two part process • Transcription • This is when a gene is transcribed (copied) • DNA gene copied into mRNA • Translation • This is when the genetic code is translated into a protein • mRNA message translated into amino acids • Amino acid chain shaped into final protein product

  21. Transcription 1. RNA Polymerase (an enzyme) binds to a gene on the DNA • RNA polymerase separates the two strands of DNA

  22. Transcription 2. One of the separated DNA strands is copied • This DNA strand is known as the TEMPLATE 3. RNA Polymerase moves along the DNA template and adds the complementary RNA nucleotide

  23. Transcription 4. RNA polymerase continues until it reaches the end of the gene 5. RNA Polymerase releases DNA and gene copy (mRNA template) • DNA strands bond back together, goes back to double helix • mRNA template will leave the nucleus and go to a ribosome

  24. Transcription

  25. Translation • Once the mRNA reaches a ribosome, the genetic message will be translated into a protein • The ribosome will scan down the mRNA strand, translating each codon into an amino acid • tRNA transfers each amino acid into the proper place based on the mRNA message • Remember: • A CODON (in mRNA) codes for one amino acid • Each amino acid is transferred in place by tRNA • ANTICODON – in tRNA, complementary to codon • PROTEIN – polymer made up of monomers of amino acids

  26. Translation

  27. Translation • mRNAleaves nucleus and goes to a ribosome to begin protein synthesis • Ribosome will attach to the end of the mRNA. The ribosome will begin to move down the mRNA template. • tRNAwill also begin to transport amino acids (floating in cytosol) to ribosome • Each amino acid is carried by a different tRNA

  28. Translation 3. The ribosome will "scan" down the mRNA template until the ribosome reaches the start codon of mRNA. • When the ribosome reaches the start codon (AUG), the ribosome will stop moving. • tRNAwith the anticodon (UAC) can bond with the start codon. • tRNAadds first amino acid of the chain: methionine (MET)

  29. Translation 4. After the first amino acid is attached, the ribosome will move down to the next codon. The next codon will be translated. • tRNA will attach the amino acid • MET and the second amino acid will bond together • Peptide bonds hold the amino acids together • Peptide Bond – covalent bond between amino acids 5. Ribosome will continue to move down the mRNA strand, stopping at each codon. • tRNA attaches to each codon and adds the correct amino acid. • The amino acids are attached in a chain by peptide bonds.

  30. Translation 6. When the ribosome reaches the “STOP” codon, no more amino acids are added • "STOP" codons (UAA, UAG, UGA) don’t code for an amino acid 7. Long chain of amino acids is released • Long chain of amino acids – Polypeptide 8. Ribosome separates from the mRNA strand. 9. Polypeptide will coil/fold into its final shape, it will then be known as a protein

  31. End of Lecture 3

  32. Unit 7 • Lecture 4 • Topic: • Cell Differentiation • Gene Expression • Covers: • Chapter 11 • Page 209

  33. Cell Differentiation • Only certain sections of the DNA molecule code for a gene • A gene is a section of DNA that codes for a protein • The longer the strand of DNA, the more genes it can store • Non-coding Region – Sections of DNA that do not code for proteins

  34. Cell Differentiation • In a multicellular organism, every cell in the body has the same DNA • Every cell in the body came from one cell – a fertilized egg (embryo) • Embryo divides numerous times to add new body cells • Uses process of mitosis to add new body cells (Somatic Cells) • This means that every cell in our body has the same genes • In humans, each somatic cell is a diploid cell and has 46 chromosomes

  35. Cell Differentiation • Every cell in a multicellular organism contains all of the organism’s genes • But, each cell does not need to use every gene to function properly. • Differentiated(specialized) cells only use the genes necessary for that cell type to function • Only makes the necessary proteins for that cell type • Cells can regulate which proteins they make by controlling which genes are activated and used to make proteins.

  36. Gene Expression • GENE EXPRESSION - activation of a gene that results in the formation of a protein. • A gene is expressed when it is copied into RNA • Control of gene expression is very important in embryo development and as cells are becoming specialized • Before cells become specialized, they are known as Stem Cells • Stem cells activate certain genes & begin to become specialized • This causes the cell to change its shape to take on its final specialized form and function • Remember: Our body is made up of over 200 different types of cells! Each cell/tissue type has its own unique form & function

  37. End of Lecture 4

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