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1. DNA, RNA structure 2. DNA replication 3. Transcription, translation

1. DNA, RNA structure 2. DNA replication 3. Transcription, translation. DNA and RNA are polymers of nucleotides. DNA is a nucleic acid, made of long chains of nucleotides. Phosphate group. Nitrogenous base. Nitrogenous base (A, G, C, or T). Sugar. Phosphate group. Nucleotide.

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1. DNA, RNA structure 2. DNA replication 3. Transcription, translation

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  1. 1. DNA, RNA structure 2. DNA replication 3. Transcription, translation

  2. DNA and RNA are polymers of nucleotides • DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Nitrogenous base(A, G, C, or T) Sugar Phosphategroup Nucleotide Thymine (T) Sugar(deoxyribose) DNA nucleotide Figure 10.2A Polynucleotide Sugar-phosphate backbone

  3. DNA has four kinds of bases, A, T, C, and G Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Pyrimidines Purines Figure 10.2B

  4. different sugar • U instead of T • Single strand, usually • RNA is also a nucleic acid Nitrogenous base(A, G, C, or U) Phosphategroup Uracil (U) Sugar(ribose) Figure 10.2C, D

  5. DNA is a double-stranded helix • James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin Figure 10.3A, B

  6. Hydrogen bond • Hydrogen bonds between bases hold the strands together: A and T, C and G Ribbon model Partial chemical structure Computer model Figure 10.3D

  7. Untwisting and replication of DNA • each strand is a template for a new strand helicase DNA polymerase Figure 10.4B

  8. 5 end 3 end P • Each strand of the double helix is oriented in the opposite direction P P P P P P P 3 end 5 end Figure 10.5B

  9. 3 DNA polymerasemolecule 5 5 end Daughter strandsynthesizedcontinuously Parental DNA 5 3 Daughter strandsynthesizedin pieces • DNA polymerase works in only one direction 3 P 5 • Telomere sequences are lost with each replication. • Cancer, aging telomeres 5 P 3 DNA ligase Overall direction of replication Figure 10.5C

  10. The information constituting an organism’s genotype is carried in its sequence of bases • The DNA is transcribed into RNA, which is translated into the polypeptide DNA TRANSCRIPTION RNA TRANSLATION Protein Figure 10.6A

  11. Transcription produces genetic messages in the form of mRNA RNA nucleotide RNApolymerase Direction oftranscription Templatestrand of DNA Newly made RNA Figure 10.9A

  12. RNA polymerase DNA of gene Promoter DNA Terminator DNA Initiation • RNA nucleotides line up along one strand of DNA, following the base-pairing rules • single-stranded messenger RNA peels away and DNA strands rejoin • In transcription, DNA helix unzips Elongation Area shownin Figure 10.9A Termination GrowingRNA Completed RNA RNApolymerase Figure 10.9B

  13. Eukaryotic RNA is processed before leaving the nucleus Exon Intron Exon Intron Exon DNA TranscriptionAddition of cap and tail • Noncoding segments, introns, are spliced out • A cap and a tail are added to the ends Cap RNAtranscriptwith capand tail Introns removed Tail Exons spliced together mRNA Coding sequence NUCLEUS CYTOPLASM Figure 10.10

  14. Translation of nucleic acids into amino acids • The “words” of the DNA “language” are triplets of bases called codons • The codons in a gene specify the amino acid sequence of a polypeptide

  15. Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid Figure 10.7

  16. Virtually all organisms share the same genetic code “unity of life” Second Base U C A G UUU UCU UAU UGU U tyr phe cys UUC UCC UAC UGC C ser U UUA UCA UAA stop UGA stop A leu UUG UCG UAG stop UGG trp G CUU CCU CAU CGU U his CUC CCC CAC CGC C pro arg leu C CUA CCA CAA CGA A gln CUG CCG CAG CGG G First Base Third Base AUU ACU AAU AGU U ser asn AUC ACC AAC AGC C ile thr A AUA ACA A AAA AGA lys arg AGG AUG ACG AAG G met (start) GUU GCU GAU GGU U asp GUC GCC GAC GGC C val G ala gly GUA GCA GAA GGA A glu GUG GCG GAG GGG G

  17. Transcribed strand • An exercise in translating the genetic code DNA Transcription RNA Startcodon Stopcodon Translation Polypeptide Figure 10.8B

  18. Transfer RNA molecules serve as interpreters during translation Amino acid attachment site • In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptide • The process is aided by transfer RNAs Hydrogen bond RNA polynucleotide chain Anticodon Figure 10.11A

  19. Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other Amino acidattachment site Anticodon Figure 10.11B, C

  20. An initiation codon marks the start of an mRNA message AUG = methionine Start of genetic message End Figure 10.13A

  21. mRNA, a specific tRNA, and the ribosome subunits assemble during initiation Largeribosomalsubunit Initiator tRNA P site A site Startcodon Small ribosomalsubunit mRNA 1 2 Figure 10.13B

  22. Elongation • The mRNA moves a codon at a time relative to the ribosome • A tRNA pairs with each codon, adding an amino acid to the growing polypeptide • A STOP codon causes the mRNA-ribosome complex to fall apart

  23. Amino acid Polypeptide Asite P site Anticodon mRNA 1 Codon recognition mRNAmovement Stopcodon Newpeptidebond 2 Peptide bond formation 3 Translocation Figure 10.14

  24. Table 14.2 Types of RNA Type of RNA Functions in Function Messenger RNA (mRNA) Nucleus, migrates to ribosomes in cytoplasm Carries DNA sequence information to ribosomes Transfer RNA (tRNA) Cytoplasm Provides linkage between mRNA and amino acids; transfers amino acids to ribosomes Cytoplasm Ribosomal RNA (rRNA) Structural component of ribosomes

  25. Review: The flow of genetic information in the cell is DNARNAprotein • The sequence of codons in DNA spells out the primary structure of a polypeptide • Polypeptides form proteins that cells and organisms use

  26. Mutations can change the meaning of genes • Mutations are changes in the DNA base sequence • caused by errors in DNA replication or by mutagens • change of a single DNA nucleotide causes sickle-cell disease

  27. Normal hemoglobin DNA Mutant hemoglobin DNA mRNA mRNA Normal hemoglobin Sickle-cell hemoglobin Glu Val Figure 10.16A

  28. NORMAL GENE • Types of mutations mRNA Protein Met Lys Phe Gly Ala BASE SUBSTITUTION Met Lys Phe Ser Ala Missing BASE DELETION Met Lys Leu Ala His Figure 10.16B

  29. Chromosomal changes can be large or small Deletion Homologouschromosomes Duplication Inversion Reciprocaltranslocation Nonhomologouschromosomes Figure 8.23A, B

  30. TRANSCRIPTION DNA Stage mRNA istranscribed from aDNA template. 1 mRNA RNApolymerase • Summary of transcription and translation Amino acid TRANSLATION Stage Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP. 2 Enzyme tRNA Initiator tRNA Anticodon Stage Initiation of polypeptide synthesis 3 Largeribosomalsubunit The mRNA, the first tRNA, and the ribosomal subunits come together. Start Codon Smallribosomalsubunit mRNA Figure 10.15

  31. Newpeptidebondforming Growing polypeptide Stage Elongation 4 A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosome, one codon at a time. Codons mRNA Polypeptide Stage Termination 5 The ribosome recognizes a stop codon. The poly-peptide is terminated and released. Stop Codon Figure 10.15 (continued)

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