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Chapter 9 DNA and the Molecular Structure of Chromosomes © John Wiley & Sons, Inc.

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Presentation on theme: "Chapter 9 DNA and the Molecular Structure of Chromosomes © John Wiley & Sons, Inc."— Presentation transcript:

1 Chapter 9 DNA and the Molecular Structure of Chromosomes © John Wiley & Sons, Inc.

2 Chapter Outline  Functions of the Genetic Material  Proof That Genetic Information Is Stored in DNA  The Structures of DNA and RNA  Chromosome Structure in Prokaryotes and Viruses  Chromosome Structure in Eukaryotes © John Wiley & Sons, Inc.

3 Functions of the Genetic Material The genetic material must replicate, control the growth and development of the organism, and allow the organism to adapt to changes in the environment. © John Wiley & Sons, Inc.  Genotypic Function: Replication  Phenotypic Function: Gene Expression  Evolutionary Function: Mutation (Gene modifications)

4 Chromosomes  Genes are located on chromosomes.  Chromosomes contain proteins and nucleic acids.  The nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). © John Wiley & Sons, Inc.

5 Proof that Genetic Information is Stored in DNA In most organisms, the genetic information is encoded in DNA. In some viruses, RNA Is the genetic material. Proteins? © John Wiley & Sons, Inc. Chromosomes-nuclear fraction-DNA Cytosol-proteins-RNA

6 DNA Mediates Transformation © John Wiley & Sons, Inc. Griffith’s experiment (in vivo) Mice Streptococcus pneumoniae --type IIIS (virulent) --type IIR (avirulent) “Transforming principles” Sia and Dawson’s experiment (in vitro)

7 DNA Mediates Transformation © John Wiley & Sons, Inc. Griffith’s experiment (in vivo) Mice Streptococcus pneumoniae --type IIIS (virulent) --type IIR (avirulent) “Transforming principles” Sia and Dawson’s experiment (in vitro)

8 © John Wiley & Sons, Inc. Avery, MacLeod and McCarty’s experiment (in vitro)

9 The Genetic Material of Bacteriophage T2 is DNA © John Wiley & Sons, Inc. Hesley-Chase’s experiment (in vitro) > Transfection ( Infection)

10 The Genetic Material of Tobacco Mosaic Virus (TMV) is RNA © John Wiley & Sons, Inc. Retroviruses ( RNA------> DNA) (in vitro)

11 The genetic information of most living organisms is stored in deoxyribonucleic acid (DNA). In some viruses, the genetic information is present in ribonucleic acid (RNA). © John Wiley & Sons, Inc.

12 The Structures of DNA and RNA DNA is double-stranded, with adenine paired with thymine and guanine paired with cytosine. RNA is usually single-stranded and contains uracil in place of thymine. © John Wiley & Sons, Inc.

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14 Deoxyribonucleotides © John Wiley & Sons, Inc.

15 Structure of a Polynucleotide Chain © John Wiley & Sons, Inc. DNA composition: [A]=[T] ; [C]=[G]

16 Chargaff’s Rules © John Wiley & Sons, Inc. %A = %T and %G = %C. %A ~ %T and %G ~ %C are valid for each of the two DNA strands methyltransferases methylate and/or deaminate

17 Structure of a Polynucleotide Chain © John Wiley & Sons, Inc. DNA composition: [A]=[T] ; [C]=[G] X-ray Diffraction Pattern of DNA

18 The Double Helix © John Wiley & Sons, Inc. Phosphodiester [C-O-P-O-C] Polynucleotide chain

19 © John Wiley & Sons, Inc.

20 Complementary and Antiparallel

21 © John Wiley & Sons, Inc.

22 DNA Structure  Complementary Base Pairs (A with T, G with C)  Anti-parallel Strands  Right-handed double helix (B-DNA) © John Wiley & Sons, Inc.

23 DNA replicationDNA-RNA duplexes Elevated content of C:G

24 DNA Structure: Supercoils © John Wiley & Sons, Inc. Unique structure of a DNA molecule Is produced after one or both strand of DNA are cleaved DNA will rotate or twist

25 © John Wiley & Sons, Inc.

26 DNA usually exists as a double helix, with the two strands held together by hydrogen bonds between the complementary base pairs: adenine paired with thymine and guanine paired with cytosine. The complementarity of the two strands of a double helix makes DNA uniquely suited to store and transmit genetic information. © John Wiley & Sons, Inc.

27 The two strands of a DNA double helix have opposite chemical polarity. RNA usually exists as a single-stranded molecule containing uracil instead of thymine. The functional DNA molecules in cells are negatively supercoiled. © John Wiley & Sons, Inc.

28 Chromosome Structure in Prokaryotes and Viruses The DNA molecules of prokaryotes and viruses (RNA?) are organized into negatively supercoiled domains. © John Wiley & Sons, Inc. Prokaryotes are monoploid and are part of the nucleoids. Most viruses and prokaryotes have a single set of genes stored in a single chromosome, which contains a single molecule of nucleic acid.

29 The E. coli Chromosome © John Wiley & Sons, Inc. Folded genome: is the functional state of a isolated bacterial chromosome Mild conditions (no ionic detergents) 1M salt Polyamines(-)

30 Model of E. coli Chromosome © John Wiley & Sons, Inc. folded=coiled protein Nicked=single strand

31 The DNA molecules in prokaryotic and viral chromosomes are organized into negatively supercoiled domains (loops). Bacterial chromosomes contain circular molecules of DNA segregated into 50 to 100 domains. © John Wiley & Sons, Inc.

32 Chromosome Structure in Eukaryotes Eukaryotic chromosomes contain huge molecules of DNA that are highly condensed during mitosis and meiosis. The centromeres and telomeres of eukaryotic chromosomes have unique structures. © John Wiley & Sons, Inc. Each chromosome is unineme (Theory) Each chromosome contains a single large double helix (strand) of DNA molecule

33 Chromatin Composition © John Wiley & Sons, Inc. (+) (-) Histones: H1, H2a, H2b, H3, H4 (protamines in sperm) Structural Nonhistone proteins: Non structural Regulation Nucleosomes: DNA + histones except H1

34 Nucleosomes © John Wiley & Sons, Inc.

35 Methyl groups Acetyl groups

36 Structure of the Nucleosome Core © John Wiley & Sons, Inc.

37 Human Metaphase Chromosomes © John Wiley & Sons, Inc.

38 The 30 nm Fiber © John Wiley & Sons, Inc.

39  Micrococcal nuclease releases individual nucleosomes from chromatin as particles. Endonucleases Intermediate Structures?

40 Both the 10 nm fiber and the 30 nm fiber were first seen by electron microscopy. Higher packing of the nucleosomes into “inactive heterochromatin” may involve Non-histone proteins. The path of nucleosomes in the chromatin fiber High salts H1

41 DNA Around a Scaffold of Non-histone Proteins © John Wiley & Sons, Inc. heterochromatin

42 Levels of DNA Packaging  2-nm double-stranded DNA molecule  11-nm nucleosomes  30 nm chromatin fiber  Organization around a central scaffold © John Wiley & Sons, Inc. H1

43 DNA repeats © John Wiley & Sons, Inc. Centromeric : specific repeated regions (non-coding DNA sequences= heterochromatin) of chromosome for attachment of spindle microtubules ( 5000 to bp). Satellite sequences: --Tandemly--Tandemly repeating --Non-coding DNA Alpha ( unit repeat as base pair) Beta Satellite Satellite Satellite Most satellite DNA is localized to the telomeric or the centromeric region of the chromosome

44 Telomeres  Functions of telomeres –Protect the ends of linear DNA molecules from deoxyribonucleases –Prevent fusion of chromosomes –Facilitate complete replication of the ends of linear DNA molecules  Most telomeres contain repetitive sequences and a distinct structure. © John Wiley & Sons, Inc.

45 Telomere Structure © John Wiley & Sons, Inc. -TTAGGG -500 to 3000 repeats -G-rich overhang -T-loop (D-loop) -Telomeres specific Proteins ( protection) POT1 TRF1 and 2 TIN2 and TPP1

46 Repeated DNA Sequences  Eukaryotic chromosomes contain repetitive DNA ( 15 to 80 %), Human (~50%) --Satellite bands (tandem repeats) --Transposable genetic elements (transposon) ---Retrotransposon, ---DNA transposon --Genomic island (G+C) © John Wiley & Sons, Inc.

47 The heritable factors that Mendel studied are now known as: a) Nucleic acids b) Amino acids c) Genes d) Unit factors e) Peptides Different forms of the same gene are known as: a) Peptides b) Amino acids c) Proteins d) Alleles e) Gene differences The building blocks of genes are: a) Proteins b) Amino acids c) Nucleic acids d) Lipids e) Carbohydrates

48 The main components of a membrane in a cell are: a) Lipids b) Proteins c) Carbohydrates d) Lipids and Proteins e) Lipids and Carbohydrates Prokaryotes can be characterized by: 1.The lack of a true nucleus or compartment in which the DNA is located 2. The unique cell walls composed of murein 3. The lack of mitochondria 4. All of these a) 1 b) 2 c) 3 d) 4 e) 1 and 3

49 Which large organic molecules are essential chromosome components? a) Lipids and proteins b) Proteins and nucleic acids c) Nucleic acids and polysaccharides d) Proteins and polysaccharides Which of the following is a type of nucleic acid? a) DNA b) RNA c) DNAse d) RNAse e) DNA and RNA In Sia and Dawson's 1931 experiment: a) Mice were required to demonstrate the transforming principle b) Used serum to precipitate IIIS cells from a mixture of heat-killed IIIS and living IIR cells c) They showed that mice play no direct role in the transforming principle d) Heat-killed IIR cells mixed with living IIIS cells gave rise to IIR colonies e) None of these


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