Chapter 10. The Structure and Function of DNA. Lectures by Edward J. Zalisko

Transcription

1 Chapter 10 The Structure and Function of DNA PowerPoint Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko 2013 Pearson Education, Inc.

2 DNA and RNA Structure DNA and RNA are nucleic acids. They consist of chemical units called nucleotides. A nucleotide polymer is a polynucleotide. Nucleotides are joined by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone Pearson Education, Inc.

3 Figure 10.1b Nitrogenous base (can be A, G, C, or T) Thymine (T) Phosphate group DNA nucleotide Sugar (deoxyribose)=dna

4 Figure 10.UN03 Nitrogenous base DNA Phosphate group Sugar Polynucleotide Nucleotide Nitrogenous base Sugar Number of strands DNA C G A T Deoxyribose 2 RNA C G A U Ribose 1

5 Figure 10.UN05 Gene TRANSCRIPTION TRANSLATION mrna Polypeptide DNA

6 Figure 10.1 Phosphate group Nitrogenous base Sugar DNA nucleotide Nitrogenous base (can be A, G, C, or T) Thymine (T) DNA double helix Phosphate group DNA nucleotide Sugar (deoxyribose) Polynucleotide Sugar-phosphate backbone

7 DNA and RNA Structure The sugar in DNA is deoxyribose. Thus, the full name for DNA is deoxyribonucleic acid. The sugar in RNA is ribose. Thus, the full name for RNA is ribonucleic acid Pearson Education, Inc.

8 DNA and RNA Structure The four nucleotides found in DNA differ in their nitrogenous bases. These bases are thymine (T), cytosine (C), adenine (A), and guanine (G). RNA has uracil (U) in place of thymine Pearson Education, Inc.

9 Watson and Crick s Discovery of the Double Helix James Watson and Francis Crick determined that DNA is a double helix. Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA. Rosalind Franklin produced the X-ray image of DNA Pearson Education, Inc.

10 Figure 10.3a James Watson (left) and Francis Crick

11 Figure 10.3b Rosalind Franklin X-ray images of DNA

12 Watson and Crick s Discovery of the Double Helix The model of DNA is like a rope ladder twisted into a spiral. The ropes at the sides represent the sugarphosphate backbones. Each wooden rung represents a pair of bases connected by hydrogen bonds Pearson Education, Inc.

13 Figure 10.4 Twist

14 Watson and Crick s Discovery of the Double Helix DNA bases pair in a complementary fashion: adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G) Pearson Education, Inc.

15 Figure 10.5 Hydrogen bond (a) Ribbon model (b) Atomic model (c) Computer model

16 Figure 10.6 Parental (old) DNA molecule Daughter (new) strand Parental (old) strand DNA polymerases Daughter DNA molecules (double helices)

17 DNA Replication DNA replication in eukaryotes begins at specific sites on a double helix (called origins of replication) and proceeds in both directions Pearson Education, Inc.

18 Figure 10.7 Origin of replication Parental strands Origin of replication Origin of replication Parental strand Daughter strand Bubble Two daughter DNA molecules

19 How an Organism s Genotype Determines Its Phenotype An organism s genotype is its genetic makeup, the sequence of nucleotide bases in DNA. The phenotype is the organism s physical traits, which arise from the actions of a wide variety of proteins Pearson Education, Inc.

20 How an Organism s Genotype Determines Its Phenotype DNA specifies the synthesis of proteins in two stages: 1. transcription, the transfer of genetic information from DNA into an RNA molecule and 2. translation, the transfer of information from RNA into a protein Pearson Education, Inc.

21 Figure DNA TRANSCRIPTION RNA Nucleus Cytoplasm TRANSLATION Protein

22 Figure RNA polymerase DNA of gene Promoter DNA 1 Initiation Terminator DNA RNA 2 Elongation RNA polymerase RNA nucleotides 3 Termination Growing RNA Newly made RNA Direction of transcription (a) A close-up view of transcription Template strand of DNA Completed RNA RNA polymerase (b) Transcription of a gene

23 The Processing of Eukaryotic RNA RNA processing includes adding a cap and tail consisting of extra nucleotides at the ends of the RNA transcript, removing introns (noncoding regions of the RNA), and RNA splicing, joining exons (the parts of the gene that are expressed) together to form messenger RNA (mrna) Pearson Education, Inc.

24 Figure DNA RNA transcript with cap and tail Cap Transcription Addition of cap and tail Introns removed Tail Exons spliced together mrna Coding sequence Nucleus Cytoplasm

25 From Nucleotides to Amino Acids: An Overview What is the language of nucleic acids? In DNA, it is the linear sequence of nucleotide bases. A typical gene consists of thousands of nucleotides in a specific sequence. When a segment of DNA is transcribed, the result is an RNA molecule. RNA is then translated into a sequence of amino acids in a polypeptide Pearson Education, Inc.

26 Figure Gene 1 Gene 2 DNA molecule Gene 3 DNA strand TRANSCRIPTION RNA TRANSLATION Codon Polypeptide Amino acid

27 From Nucleotides to Amino Acids: An Overview Experiments have verified that the flow of information from gene to protein is based on a triplet code. A codon is a triplet of bases, which codes for one amino acid Pearson Education, Inc.

28 The Genetic Code The genetic code is the set of rules that convert a nucleotide sequence in RNA to an amino acid sequence. Of the 64 triplets, 61 code for amino acids and 3 are stop codons, instructing the ribosomes to end the polypeptide Pearson Education, Inc.

29 First base of RNA codon Third base of RNA codon Figure UUU UUC U UUA UUG Phenylalanine (Phe) Leucine (Leu) Second base of RNA codon U C A G UCU UCC UCA UCG Serine (Ser) UAU UAC UAA UAG Tyrosine (Tyr) Stop Stop UGU UGC UGA Cysteine (Cys) Stop UGG Tryptophan (Trp) U C A G C CUU CUC CUA CUG Leucine (Leu) CCU CCC CCA CCG Proline (Pro) CAU CAC CAA CAG Histidine (His) Glutamine (Gln) CGU CGC CGA CGG Arginine (Arg) U C A G A AUU AUC AUA AUG Isoleucine (Ile) Met or start ACU ACC ACA ACG Threonine (Thr) AAU AAC AAA AAG Asparagine (Asn) Lysine (Lys) AGU AGC AGA AGG Serine (Ser) Arginine (Arg) U C A G G GUU GUC GUA GUG Valine (Val) GCU GCC GCA GCG Alanine (Ala) GAU GAC GAA GAG Aspartic acid (Asp) Glutamic acid (Glu) GGU GGC GGA GGG Glycine (Gly) U C A G

30 Transfer RNA (trna) Transfer RNA (trna) acts as a molecular interpreter, carries amino acids, and matches amino acids with codons in mrna using anticodons, a special triplet of bases that is complementary to a codon triplet on mrna Pearson Education, Inc.

31 Figure 10.12

32 Figure Cap Start of genetic message End Tail

33 Figure Amino acid attachment site Hydrogen bond RNA polynucleotide chain trna polynucleotide (ribbon model) Anticodon trna (simplified representation)

34 Figure trna binding sites P site A site Growing polypeptide Next amino acid to be added to polypeptide mrna binding site Large subunit Small subunit Ribosome mrna trna (a) A simplified diagram of a ribosome Codons (b) The players of translation

35 Ribosomes Ribosomes are organelles that coordinate the functions of mrna and trna and are made of two subunits. Each subunit is made up of proteins and a considerable amount of another kind of RNA, ribosomal RNA (rrna) Pearson Education, Inc.

36 Ribosomes A fully assembled ribosome holds trna and mrna for use in translation Pearson Education, Inc.

37 Figure Polypeptide Amino acid P site mrna Anticodon A site 1 Codons Codon recognition ELONGATION Stop codon 2 New peptide bond Peptide bond formation mrna movement 3 Translocation

38 Review: DNA RNA Protein In a cell, genetic information flows from DNA to RNA in the nucleus and RNA to protein in the cytoplasm Pearson Education, Inc.

39 Review: DNA RNA Protein As it is made, a polypeptide coils and folds and assumes a three-dimensional shape, its tertiary structure. Transcription and translation are how genes control the structures and activities of cells Pearson Education, Inc.

40 Figure Transcription RNA polymerase Nucleus mrna DNA Tail Intron 2 Intron RNA processing mrna Cap Anticodon Codon 5 Elongation Polypeptide Amino acid trna A Ribosomal subunits Stop codon Anticodon 3 ATP Enzyme Amino acid attachment 4 Initiation of 6 translation Termination

41 Mutations A mutation is any change in the nucleotide sequence of DNA. Mutations can change the amino acids in a protein. Mutations can involve large regions of a chromosome or just a single nucleotide pair, as occurs in sickle-cell disease Pearson Education, Inc.

42 Figure Normal hemoglobin DNA Mutant hemoglobin DNA mrna mrna Normal hemoglobin Glu Sickle-cell hemoglobin Val

43 Figure 10.UN07

44 Figure 10.22a Met Lys Phe Gly Ala mrna and protein from a normal gene Met Lys Phe Ser Ala (a) Base substitution

45 Figure 10.22b Met Lys Phe Gly Ala mrna and protein from a normal gene Deleted Met Lys Leu Ala (b) Nucleotide deletion

46 Figure 10.22c Met Lys Phe Gly Ala mrna and protein from a normal gene Inserted Met Lys Leu Trp Arg (c) Nucleotide insertion

47 Mutagens Mutations may result from errors in DNA replication or recombination or physical or chemical agents called mutagens. Mutations are often harmful but are useful in nature and the laboratory as a source of genetic diversity, which makes evolution by natural selection possible Pearson Education, Inc.

48 Figure 10.23

49 VIRUSES AND OTHER NONCELLULAR INFECTIOUS AGENTS Viruses share some, but not all, characteristics of living organisms. Viruses possess genetic material in the form of nucleic acids wrapped in a protein coat, are not cellular, and cannot reproduce on their own Pearson Education, Inc.

50 Bacteriophages Bacteriophages, or phages, are viruses that attack bacteria. Phages consist of a molecule of DNA, enclosed within an elaborate structure made of proteins Pearson Education, Inc.

51 Figure Head Bacteriophage (200 nm tall) Tail Tail fiber Bacterial cell DNA of virus Colorized TEM

52 Animal Viruses Viruses that infect animals cells are a common cause of disease and may have RNA or DNA genomes. Many animal viruses have an outer envelope made of phospholipid membrane, with projecting spikes of protein Pearson Education, Inc.

53 Figure Protein spike Membranous envelope RNA Protein coat

54 Animation: Simplified Viral Reproductive Cycle Right click slide / select Play 2013 Pearson Education, Inc.