Classical and Modern Genetics

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1 Classical and Modern Genetics Chapter 23 Great Idea: All living things use the same genetic code to guide the chemical reactions in every cell. 1

2 Chapter Outline Classical Genetics DNA and the Birth of Molecular Genetics The Genetic Code 2

3 Genetics of Inheritance Classical or Mendelian genetics (Gregory Mendel) Competing hypotheses Blended inheritance Particulate inheritance Testing the hypotheses Flower color in peas (1 parent with red flowers and 2 nd parent with white flowers) Results: two classes of flowers Red (300 seedlings) White (100 seedlings) Conclusion: Support for particulate theory; reject blended theory Specific quantitative data: 3:1 ratio 3

4 iclicker Question If you were to cross rabbits that were black with rabbits that were white and the offspring were either white or black, this outcome would support the theory of. A particulate inheritance B conspicuous inheritance C Lamarckian inheritance D blended inheritance E none of the above 4

5 iclicker Question The studies of Gregor Mendel in the mid 1860 s provide data in support of the theory of particulate theory of inheritance. The other notable observation of Mendel was the quantitative data showing a ratio of in the offspring of pea plant flower color. A. blended B. 3:1 C. 1:1 D.50:50 5 E. 1:4.632

6 Mendelian Genetics (1860 s) Gene trait determined by a sequence of DNA Allele - alternative versions of the same gene (e.g., normal hemoglobin versus sickle cell hemoglobin) Dominant allele (e.g., red flower color; brown eyes) Recessive allele (e.g., white flower color; blue eyes) Chromosomes physical packaging of genes in nucleus Pairs of chromosomes (homologous pair) Genome all of the genes of an organism in the nucleus 6

7 Classical Genetics Mendel Basic laws of inheritance Classic pea plant experiments Purebred Hybrid Results First generation Second generation Gene Dominant Recessive 7

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9 Rules of Classical Genetics Traits (genes) are passed from parent to offspring mechanism unknown Two genes for each trait One from each parent There are dominant and recessive genes Dominant expressed 9

10 Qualitative Qualitative versus Quantitative Genetics observational Quantitative Predictive model Used to trace genetic disease 10

11 iclicker Question The study of ways in which biological information is passed from one generation to the next is called A ancestry B husbandry C paleontology D genetics 11

12 iclicker Question The offspring of two different strains are called: A hybrids B purebred C mutants D Mendelian populations 12

13 iclicker Question The unit of inheritance, invented by Mendel, is now called the: A hybrid B parental strain C gene D dominant characteristic E Mendel 13

14 iclicker Question In human beings, dark hair and eye color are dominant over light. A True B False 14

15 iclicker Question Each offspring has only one gene for each trait. A True B False 15

16 DNA and the Birth of Molecular Genetics 16

17 Nucleotides: The Building Blocks of Nucleic Acids Nucleotide Three molecules Sugar DNA: deoxyribose RNA: ribose Phosphate ion Base Adenine (A) Guanine (G) Cytosine (C) Thymine (T) 17

18 DNA Structure Join nucleotides Alternating phosphate and sugar DNA 2 strands of nucleotides Joined by base pairs Bonding pattern Adenine:Thymine Cytosine:Guanine 18

19 DNA Structure 19

20 RNA Structure Differences One string of nucleotides Sugar is ribose Thymine replaced by uracil Uracil (U) bonds with adenine 20

21 The Replication of DNA DNA replication Occurs before mitosis & meiosis Process DNA double helix splits New bases bond to exposed bases Result Two identical DNA strands 21

22 iclicker Question Meiosis produces sex cells with half the usual number of chromosomes. These cells are called A gametes B nucleic acids C nucleotides 22

23 iclicker Question Nucleic acids such as DNA and RNA are polymers of A amino acids B monosaccharides C nucleotides D lipids 23

24 iclicker Question What three small molecules combine to form a nucleotide? A a sugar, a lipid, and an acid B a sugar, a phosphate and a base C a lipid, a base and an amino acid D a nucleus, a sugar and a base E a nucleus, a leonid and a tide 24

25 iclicker Question What structural feature gives DNA its helical shape (double helix)? A the phosphates can form ionic bonds B the sugars have covalent bonds C the bases can form hydrogen bonds D the strong force between bases 25

26 Gene 26

27 DNA to Genes to Chromosomes Gene 27

28 Chromosomes and Alleles 28

29 Genetics of Humans - Sex Sex determination associated with one pair of chromosomes (Pair No. 21) x chromosome y chromosome Female: 2 x chromosomes (X + X) Male: 1 x and 1 y chromosome (X + Y) Female produces x chromosome eggs Male produces both x and y chromosome sperm Who determines the sex of offspring? 29

30 Transcription of DNA Transcription Information transport Uses RNA Process Unzip DNA RNA binds to exposed bases RNA moves out of nucleus (mrna) 30

31 The Synthesis of Proteins trna Reads message Structure Amino acid 3 bases Process mrna moves to ribosome rrna aligns mrna and trna trna matches codon on mrna Amino acid chain forms Basis for protein 31

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34 Protein synthesis cont. One gene codes for one protein Protein drives chemical process in cell DNA Introns Exons All living things on Earth use the same genetic code 34

35 Mutations and DNA Repair Mutations Change in DNA of parent Causes Nuclear radiation X-rays UV light DNA Repair 10,000 hits per day Cells repair damage 35

36 Why Are Genes Expressed? Gene control Turning genes on and off Each cell contains same genes Not all cells have same function Certain genes activated Scientists currently studying how 36

37 Genetics of Humans: Sex-Linked Traits Some traits more common in one sex Examples Color blindness: males Baldness: males Hemophilia: males 37

38 Human Genome and Genetic Differences 38

39 Viruses Virus Not alive No metabolism Cannot reproduce on own Structure Short DNA or RNA Protein coating How it works Taken into cell Takes over cell Produces more copies Kills cell 39

40 HIV Human Immunodeficiency Virus (HIV) Contains RNA Codes back to DNA DNA incorporated into cell Makes new viruses Cell dies Complex Two protein coats Outer coat fits T cell receptors Inner coat encloses RNA 40

41 Viral Epidemics Viruses Cannot use medication Use vaccination Viruses evolve rapidly HIV Influenza SARS Bird flu 41

42 iclicker Question RNA is different from DNA in that uracil (U) replaces which base? A adenine B guanine C cytosine D thymine 42

43 iclicker Question Making a copy of DNA is called: A replication B transcription C translation 43

44 iclicker Question Forming a strand of RNA, using the code on a segment of DNA is called: A replication B transcription C translation 44

45 iclicker Question Converting the code on a strand of RNA into a protein is called: A replication B transcription C translation 45

46 iclicker Question All living things on Earth use the same genetic code. A True B False 46

47 iclicker Question The sequence of all the base pairs in all the chromosomes is known as an organism s A DNA map B phagocyte C genome 47

48 iclicker Question If it were possible to determine which genetic diseases you might develop by having your DNA sequence analyzed, would you do this? A Yes B No 48

49 iclicker Question The number of chromosomes in any cell of your body (except for gametes) is. A 16 B 32 C 41 D 46 E None of the above 49

50 iclicker Question In genetic crosses, the re-current quantitative ratio of 3:1 among offspring supports the presence of copy/copies of each gene in an organism. A four B three C two D one 50

51 Molecular Genetics Structure of DNA and RNA information storage, transmission and expression Replication of the information copying/duplication Transcription of the information transcribing Translation of the information expressing as proteins 51

52 iclicker Question In the following figure, the information process linking the DNA to RNA (see white arrow) is called. A replication B transcription C translation D gene splicing 52

53 Molecular Genetics: Structure of DNA and RNA DNA Deoxyribonucleic acid (nucleus) RNA Ribonucleic acid (protoplasm) Monomer nucleotides (N=5) Guanine (always binds to Cytosine - G:C) Adenine (always binds to Thymine - A:T) Cytosine (always binds to Guanine - C:G) Thymine (always binds to Adenine - A:T) Uracil (T replacement in RNA) Polymer polynucleotide (DNA & RNA) 53

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55 Relating Chromosomes to the DNA Helix 55

56 Sequence of Nucleotides and Genes Linear sequences of nucleotides Gene: sequence of nucleotides responsible for a specific traits (e.g., eye color; hemoglobin and sickle cell anemia) 56

57 Molecular Genetics: A Single Gene Exact sequence of nucleotides is important A T T A G C G G T A T G C C G G T T A A G A T C C G A T T A G C G G T A C G C C G G T T A A G A T C C G Any change in sequence changes the information ( RAT to CAT ) and constitutes a mutation 57

58 iclicker Question In a DNA polynucleotide, the base sequence is T-A-A-G-C-T. Which base sequence would be bonded to this section of a complementary strand of DNA polynucleotide? A B C D E A-C-G-T-A-A A-C-G-U-U-A A-G-C-T-T-A U-G-C-A-A-U A-T-T-C-G-A 58

59 iclicker Question An mrna sequence is 300 nucleotides in length. The number of amino acids in the protein translated from this mrna is. A. 50 B. 100 C. 150 D. 200 E

60 Molecular Genetics: Replication Replication: process of duplicating DNA to produce a new and exact copy with fidelity includes spell checking 60

61 Molecular Genetics: Transcription Process whereby information in DNA is transcribed into another type of message called mrna (message RNA) mrna made in nucleus and subsequently shuttled to protoplasm In protoplasm, mrna finds its way to the ribosome (where protein synthesis occurs) 61

62 Compartmentation: Ribosome 62

63 Molecular Genetics: Translation Process whereby information in mrna is transcribed into proteins (polypeptides) Monomer: amino acids (e.g., lab exercise) Location: ribosome for protein synthesis Genetic code: specificity and fidelity Three consecutive nucleotides of mrna used to call in unique amino acid 63

64 Translation and the Genetic Code Sequence of Amino Acids: Polypeptide Genetic Code mrna Ribosome 64

65 Genetic Code and Evolution Fidelity in copying information Specificity in information Expression of gene via manufacturing of polypeptide leading to protein (e.g., enzyme) Genetic Code is conserved in evolution all organisms use the exact same coding process Example of Genetic Code: laboratory exercise using hemoglobin across multiple species 65

66 Genetics on the Cutting Edge Genetic Counseling (probability of offspring with particular traits) Forensic Sciences (e.g., CSI TV series) Genetic Engineering (e.g., starlight strain of corn) GMO s (Genetically Modified Organisms) Genetic Sleuthing Human applications (e.g., ice man in the Alps + 5,000 years) Pharmaceuticals Toxicology of drugs and chemicals (e.g., Celebrex) 66

67 Genetic Counseling 67

68 Genetic Counseling using Gene Chips 68

69 Forensic Sciences 69

70 GMO s 70

71 Genetic Sleuthing: Ice Man of the Alps 71

72 Take-Home Messages Inheritance of traits is best explained by the hypothesis that traits are not blended but expressed as distinct units called genes and alleles; this is the particulate theory of inheritance The following two sequences underpin all of molecular genetics DNA Transcription mrna Translation Polypeptide Protein DNA Replication DNA Genetic code is a process common to all organisms and is prima facia evidence for evolution Application of molecular techniques is substantial and will affect dramatically your lives and that of your children 72

BIOLOGY 111. CHAPTER 6: DNA: The Molecule of Life

BIOLOGY 111. CHAPTER 6: DNA: The Molecule of Life BIOLOGY 111 CHAPTER 6: DNA: The Molecule of Life Chromosomes and Inheritance Learning Outcomes 6.1 Describe the structure of the DNA molecule and how this structure allows for the storage of information,