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Review

Review. Base Pairing Rule. Watson and Crick showed that DNA is a double helix A (adenine) pairs with T (thymine) C (cytosine) pairs with G (guanine). DNA Replication. Steps in DNA Replication. Occurs when chromosomes duplicate (make copies)

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Review

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Presentation Transcript

  1. Review

  2. Base Pairing Rule • Watson and Crick showed that DNA is a double helix • A (adenine) pairs with T (thymine) • C (cytosine) pairs with G (guanine)

  3. DNA Replication

  4. Steps in DNA Replication • Occurs when chromosomes duplicate (make copies) • The enzyme DNA polymerase adds new nucleotides • Each old strand of nucleotides serves as a template for each new strand

  5. Another View of Replication

  6. RNA

  7. RNA Differs from DNA 1. RNA has a sugar ribose 2. RNA contains the base uracil (U) 3. RNA molecule is single-stranded

  8. Structure of RNA

  9. . Three Types of RNA • Messenger RNA (mRNA)carries genetic information to the ribosomes • Transfer RNA (tRNA)transfers amino acids to the ribosomes where proteins are synthesized • Ribosomal RNA (rRNA),along with protein, makes up the ribosomes

  10. RNA • RNA – Ribonucleic Acid • Single stranded nucleotide chain • Single stranded helix • DNA’s Thymine is REPLACED by Uracil • A & T “break up” because of the new guy: U • But C & G are still 4-eva

  11. mRNA - messenger RNA • Used for protein synthesis • Codes for amino acid sequence • made from DNA • travels • Nucleus  Cytoplasm  Ribosomes DNA: GACCATAGC mRNA: Codon: group of 3 bases “GAC” or “CAT” CUGGUAUCG

  12. mRNA codon “UGG” • tRNA – transfer RNA • Brings specific amino acid to the growing amino acid chain • “fetching puppy” Anticodon “ACC” Corresponding Amino Acid

  13. The Genetic Code • Use mRNA codons with chart!!!!

  14. DNA = AAT CCG GGG ATC ATG CCG • mRNA

  15. Ribosomal RNA (rRNA) • rRNA is a single strand • Globular in shape • Site of protein Synthesis • “docking station”

  16. Transfer RNA (tRNA) • Clover-leaf shape • Single stranded molecule folded like a “t” • attachment site at one end for an amino acid • Opposite end has three nucleotide bases called the anticodon

  17. Transfer RNA anticodon

  18. Making a Protein

  19. Argenine – Leucine – Aspartic Acid Proteins = polypeptide = amino acid chain Peptide Bonds – amino acids are connected together through peptide bonds

  20. Transcription • Transcription – stage of protein synthesis where instructions for making a protein are transferred to an RNA molecule • DNA  mRNA : transcription • Translation – stage of protein synthesis when the information in mRNA is used to make proteins • mRNA  amino acid chain

  21. Genes & Proteins • Proteins are made of amino acids linked together by peptide bonds • 20 different amino acids exist • Amino acids chains are called polypeptides • Segment of DNA that codes for the amino acid sequence in a protein are called genes

  22. Two Parts of Protein Synthesis • Transcription makes an RNA molecule complementary to a portion of DNA • Translationoccurs when the sequence of bases of mRNA DIRECTS the sequence of amino acids in a polypeptide

  23. Genetic Code • DNA contains a triplet code • Every three bases on DNA stands for ONE amino acid • Each three-letter unit on mRNA is called a codon • Most amino acids have more than one codon! • There are 20 amino acids with a possible 64 different triplets • The code is nearly universal among living organisms

  24. Always… use mRNA to decode!!!

  25. Name the Amino AcidsUse the code by reading from the center to the outside • GGG? • UCA? • CAU? • GCA? • AAA?

  26. Remember the Complementary Bases On DNA: A-T C-G On RNA: A-U C-G

  27. Codons and Anticodons • The 3 bases of an anticodon are complementary to the 3 bases of a codon • Example: Codon ACU Anticodon UGA UGA ACU

  28. Transcription Translation

  29. PROTEIN SYNTHESIS

  30. Protein Synthesis • The production (synthesis) of polypeptide chains (proteins) • Two phases:Transcription & Translation • mRNA must be processed before it leaves the nucleus of eukaryotic cells

  31. Nuclear membrane DNA Transcription Pre-mRNA RNA Processing mRNA Ribosome Translation Protein DNA  RNA Protein Eukaryotic Cell

  32. Pathway to Making a Protein DNA mRNA tRNA (ribosomes) Protein

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