Presentation is loading. Please wait.

Presentation is loading. Please wait.

Copyright Pearson Prentice Hall 12–1 DNA. Copyright Pearson Prentice Hall Griffith and Transformation In 1928, British scientist Fredrick Griffith was.

Similar presentations


Presentation on theme: "Copyright Pearson Prentice Hall 12–1 DNA. Copyright Pearson Prentice Hall Griffith and Transformation In 1928, British scientist Fredrick Griffith was."— Presentation transcript:

1 Copyright Pearson Prentice Hall 12–1 DNA

2 Copyright Pearson Prentice Hall Griffith and Transformation In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused pneumonia. He isolated two different strains of pneumonia bacteria from mice and grew them in his lab.

3 Copyright Pearson Prentice Hall Griffith and Transformation Griffith made two observations: (1) The disease-causing strain of bacteria grew into smooth colonies on culture plates. (2) The harmless strain grew into colonies with rough edges.

4 Copyright Pearson Prentice Hall Griffith and Transformation Griffith's Experiments Griffith set up four individual experiments. Experiment 1: Mice were injected with the disease-causing strain of bacteria. The mice developed pneumonia and died.

5 Copyright Pearson Prentice Hall Griffith and Transformation Experiment 2: Mice were injected with the harmless strain of bacteria. These mice didn’t get sick. Harmless bacteria (rough colonies) Lives

6 Copyright Pearson Prentice Hall Griffith and Transformation Experiment 3: Griffith heated the disease- causing bacteria. He then injected the heat-killed bacteria into the mice. The mice survived. Heat-killed disease- causing bacteria (smooth colonies) Lives

7 Copyright Pearson Prentice Hall Griffith and Transformation Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died. Live disease- causing bacteria (smooth colonies) Dies of pneumonia Heat-killed disease- causing bacteria (smooth colonies) Harmless bacteria (rough colonies)

8 Copyright Pearson Prentice Hall Griffith and Transformation Griffith concluded that the heat-killed bacteria passed their disease- causing ability to the harmless strain. Live disease- causing bacteria (smooth colonies) Heat-killed disease- causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumonia

9 Copyright Pearson Prentice Hall Griffith and Transformation Transformation Griffith called this process transformation because one strain of bacteria (the harmless strain) had changed permanently into another (the disease-causing strain). Griffith hypothesized that a factor must contain information that could change harmless bacteria into disease-causing ones.

10 Copyright Pearson Prentice Hall Avery and DNA Oswald Avery repeated Griffith’s work to determine which molecule was most important for transformation. Avery and his colleagues made an extract from the heat-killed bacteria that they treated with enzymes.

11 Copyright Pearson Prentice Hall Avery and DNA The enzymes destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNA. Transformation still occurred.

12 Copyright Pearson Prentice Hall Avery and DNA Avery and other scientists repeated the experiment using enzymes that would break down DNA. When DNA was destroyed, transformation did not occur. Therefore, they concluded that DNA was the transforming factor.

13 Copyright Pearson Prentice Hall Avery and DNA Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.

14 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Alfred Hershey and Martha Chase studied viruses—nonliving particles smaller than a cell that can infect living organisms.

15 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Bacteriophages A virus that infects bacteria is known as a bacteriophage. Bacteriophages are composed of a DNA or RNA core and a protein coat.

16 Copyright Pearson Prentice Hall The Hershey-Chase Experiment They grew viruses in cultures containing radioactive isotopes of phosphorus-32 ( 32 P) and sulfur-35 ( 35 S).

17 Copyright Pearson Prentice Hall The Hershey-Chase Experiment If 35 S was found in the bacteria, it would mean that the viruses’ protein had been injected into the bacteria. Bacteriophage with suffur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

18 Copyright Pearson Prentice Hall The Hershey-Chase Experiment If 32 P was found in the bacteria, then it was the DNA that had been injected. Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium

19 Copyright Pearson Prentice Hall The Hershey-Chase Experiment Nearly all the radioactivity in the bacteria was from phosphorus ( 32 P). Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein.

20 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA is made up of nucleotides. A nucleotide is a monomer of nucleic acids made up of: Deoxyribose – 5-carbon Sugar Phosphate Group Nitrogenous Base

21 Copyright Pearson Prentice Hall The Components and Structure of DNA There are four kinds of bases in in DNA: adenine guanine cytosine thymine

22 Copyright Pearson Prentice Hall The Components and Structure of DNA Chargaff's Rules Erwin Chargaff discovered that: The percentages of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA. The percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA.

23 Copyright Pearson Prentice Hall The Components and Structure of DNA X-Ray Evidence Rosalind Franklin used X-ray diffraction to get information about the structure of DNA. She aimed an X-ray beam at concentrated DNA samples and recorded the scattering pattern of the X-rays on film.

24 Copyright Pearson Prentice Hall The Components and Structure of DNA The Double Helix Using clues from Franklin’s pattern, James Watson and Francis Crick built a model that explained how DNA carried information and could be copied. Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other.

25 Copyright Pearson Prentice Hall The Components and Structure of DNA DNA Double Helix

26 Copyright Pearson Prentice Hall

27 The Components and Structure of DNA Watson and Crick discovered that hydrogen bonds can form only between certain base pairs—adenine and thymine, and guanine and cytosine. This principle is called base pairing.

28 Copyright Pearson Prentice Hall 12–1 Avery and other scientists discovered that a.DNA is found in a protein coat. b.DNA stores and transmits genetic information from one generation to the next. c.transformation does not affect bacteria. d.proteins transmit genetic information from one generation to the next.

29 Copyright Pearson Prentice Hall 12–1 The Hershey-Chase experiment was based on the fact that a.DNA has both sulfur and phosphorus in its structure. b.protein has both sulfur and phosphorus in its structure. c.both DNA and protein have no phosphorus or sulfur in their structure. d.DNA has only phosphorus, while protein has only sulfur in its structure.

30 Copyright Pearson Prentice Hall 12–1 DNA is a long molecule made of monomers called a.nucleotides. b.purines. c.pyrimidines. d.sugars.

31 Copyright Pearson Prentice Hall 12–1 Chargaff's rules state that the number of guanine nucleotides must equal the number of a.cytosine nucleotides. b.adenine nucleotides. c.thymine nucleotides. d.thymine plus adenine nucleotides.

32 Copyright Pearson Prentice Hall 12–1 In DNA, the following base pairs occur: a.A with C, and G with T. b.A with T, and C with G. c.A with G, and C with T. d.A with T, and C with T.

33 Copyright Pearson Prentice Hall 12-2 Chromosomes and DNA Replication 12–2 Chromosomes and DNA Replication

34 Copyright Pearson Prentice Hall DNA and Chromo somes In prokaryotic cells, DNA is located in the cytoplasm. Most prokaryotes have a single DNA molecule containing nearly all of the cell’s genetic information.

35 Copyright Pearson Prentice Hall DNA and Chromo somes Chromosome E. Coli Bacterium Bases on the Chromosomes

36 Copyright Pearson Prentice Hall DNA and Chromo somes Many eukaryotes have 1000 times the amount of DNA as prokaryotes. Eukaryotic DNA is located in the cell nucleus inside chromosomes. The number of chromosomes varies widely from one species to the next.

37 Copyright Pearson Prentice Hall DNA and Chromo somes Chromosome Structure Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin. Chromatin consists of DNA tightly coiled around proteins called histones. DNA and histone molecules form nucleosomes. Nucleosomes pack together, forming a thick fiber.

38 Copyright Pearson Prentice Hall DNA and Chromo somes Eukaryotic Chromosome Structure Chromosome Supercoils Nucleosome DNA double helix Histones Coils

39 Copyright Pearson Prentice Hall DNA Replica tion Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing. In most prokaryotes, DNA replication begins at a single point and continues in two directions.

40 Copyright Pearson Prentice Hall DNA Replica tion In eukaryotic chromosomes, DNA replication occurs at hundreds of places. Replication proceeds in both directions until each chromosome is completely copied. The sites where separation and replication occur are called replication forks.

41 Copyright Pearson Prentice Hall DNA Replica tion Duplicating DNA Before a cell divides, it duplicates its DNA in a process called replication. Replication ensures that each resulting cell will have a complete set of DNA.

42 Copyright Pearson Prentice Hall DNA Replica tion During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

43 Copyright Pearson Prentice Hall

44 DNA Replica tion Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand Growth

45 Copyright Pearson Prentice Hall DNA Replica tion How Replication Occurs DNA replication is carried out by enzymes that “unzip” a molecule of DNA. Hydrogen bonds between base pairs are broken and the two strands of DNA unwind.

46 Copyright Pearson Prentice Hall DNA Replica tion Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand Growth

47 Copyright Pearson Prentice Hall DNA Replica tion The principal enzyme involved in DNA replication is DNA polymerase. DNA polymerase joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand.

48 Copyright Pearson Prentice Hall 12–2 In prokaryotic cells, DNA is found in the a.cytoplasm. b.nucleus. c.ribosome. d.cell membrane.

49 Copyright Pearson Prentice Hall 12–2 The first step in DNA replication is a.producing two new strands. b.separating the strands. c.producing DNA polymerase. d.correctly pairing bases.

50 Copyright Pearson Prentice Hall 12–2 A DNA molecule separates, and the sequence GCGAATTCG occurs in one strand. What is the base sequence on the other strand? a.GCGAATTCG b.CGCTTAAGC c.TATCCGGAT d.GATGGCCAG

51 Copyright Pearson Prentice Hall 12–2 In addition to carrying out the replication of DNA, the enzyme DNA polymerase also functions to a.unzip the DNA molecule. b.regulate the time copying occurs in the cell cycle. c.“proofread” the new copies to minimize the number of mistakes. d.wrap the new strands onto histone proteins.

52 Copyright Pearson Prentice Hall 12–2 The structure that may play a role in regulating how genes are “read” to make a protein is the a.coil. b.histone. c.nucleosome. d.chromatin.

53 Copyright Pearson Prentice Hall 12-3 RNA and Protein Synthesis 12–3 RNA and Protein Synthesis

54 Copyright Pearson Prentice Hall 12– 3 RNA and Protein Synthe sis Genes are coded DNA instructions that control the production of proteins. Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA. RNA contains coded information for making proteins.

55 Copyright Pearson Prentice Hall The Structu re of RNA There are three main differences between RNA and DNA: a.The sugar in RNA is ribose instead of deoxyribose. b.RNA is generally single-stranded. c.RNA contains uracil in place of thymine.

56 Copyright Pearson Prentice Hall Types of RNA There are three main types of RNA: a.messenger RNA b.ribosomal RNA c.transfer RNA

57 Copyright Pearson Prentice Hall Types of RNA Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins.

58 Copyright Pearson Prentice Hall Types of RNA Ribosomes are made up of proteins and ribosomal RNA (rRNA). Ribosome Ribosomal RNA

59 Protein Synthe sis DNAmolecule DNA strand (template) 3 TRANSCRIPTION Codon mRNA TRANSLATION Protein Amino acid 3 5 5

60 Copyright Pearson Prentice Hall Transcr iption DNA is copied in the form of RNA This first process is called transcription. The process begins at a section of DNA called a promoter.

61 Copyright Pearson Prentice Hall Transcr iption RNA RNA polymerase DNA

62 Copyright Pearson Prentice Hall RNA Editing Some DNA within a gene is not needed to produce a protein. These areas are called introns. The DNA sequences that code for proteins are called exons.

63 Copyright Pearson Prentice Hall RNA Editing The introns are cut out of RNA molecules. The exons are the spliced together to form mRNA. Exon Intron DNA Pre-mRNA mRNA Cap Tail

64 Copyright Pearson Prentice Hall The Genetic Code The genetic code is the “language” of mRNA instructions. The code is written using four “letters” (the bases: A, U, C, and G).

65 Copyright Pearson Prentice Hall The Genetic Code A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid.

66 Copyright Pearson Prentice Hall The Genetic Code

67 Nucleus mRNA Copyright Pearson Prentice Hall Transla tion Translation is the decoding of an mRNA message into a polypeptide chain (protein). Translation takes place on ribosomes. During translation, the cell uses information from messenger RNA to produce proteins.

68 Copyright Pearson Prentice Hall Transla tion Lysine tRNA Phenylalanine Methionine Ribosome mRNA Start codon The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA.

69 Copyright Pearson Prentice Hall Transla tion Protein Synthesis tRNA Ribosome mRNA Lysine Translation direction

70 Copyright Pearson Prentice Hall Transla tion The process continues until the ribosome reaches a stop codon. Polypeptide Ribosome tRNA mRNA

71 Copyright Pearson Prentice Hall Genes and Protein s DNA mRNA Protein Codon mRNA Alanine Arginine Leucine Amino acids within a polypeptide Single strand of DNA

72 Copyright Pearson Prentice Hall 12–3 The role of a master plan in a building is similar to the role of which molecule? a.messenger RNA b.DNA c.transfer RNA d.ribosomal RNA

73 Copyright Pearson Prentice Hall 12–3 A base that is present in RNA but NOT in DNA is a.thymine. b.uracil. c.cytosine. d.adenine.

74 Copyright Pearson Prentice Hall 12–3 The nucleic acid responsible for bringing individual amino acids to the ribosome is a.transfer RNA. b.DNA. c.messenger RNA. d.ribosomal RNA.

75 Copyright Pearson Prentice Hall 12–3 A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the a.intron. b.exon. c.promoter. d.codon.

76 A codon typically carries sufficient information to specify a(an) a.single base pair in RNA. b.single amino acid. c.entire protein. d.single base pair in DNA. Copyright Pearson Prentice Hall 12–3

77 Copyright Pearson Prentice Hall 12-4 Mutations 12–4 Mutations

78 Copyright Pearson Prentice Hall Mutati ons Mutations are changes in the genetic material.

79 Copyright Pearson Prentice Hall Kinds of Mutations Mutations that produce changes in a single gene are known as gene mutations. Mutations that produce changes in whole chromosomes are known as chromosomal mutations.

80 Copyright Pearson Prentice Hall Kinds of Mutations Gene Mutations Gene mutations involving a change in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence. Point mutations include substitutions, insertions, and deletions.

81 Copyright Pearson Prentice Hall Kinds of Mutations Substitutions usually affect no more than a single amino acid.

82 Copyright Pearson Prentice Hall Kinds of Mutations The effects of insertions or deletions are more dramatic. The addition or deletion of a nucleotide causes a shift in the grouping of codons. Changes like these are called frameshift mutations.

83 Copyright Pearson Prentice Hall Kinds of Mutations In an insertion, an extra base is inserted into a base sequence.

84 Copyright Pearson Prentice Hall Kinds of Mutations In a deletion, the loss of a single base is deleted and the reading frame is shifted.

85 Copyright Pearson Prentice Hall Kinds of Mutations Chromosomal Mutations Chromosomal mutations involve changes in the number or structure of chromosomes. Chromosomal mutations include deletions, duplications, inversions, and translocations.

86 Copyright Pearson Prentice Hall Kinds of Mutations Deletions involve the loss of all or part of a chromosome.

87 Copyright Pearson Prentice Hall Kinds of Mutations Duplications produce extra copies of parts of a chromosome.

88 Copyright Pearson Prentice Hall Kinds of Mutations Inversions reverse the direction of parts of chromosomes.

89 Copyright Pearson Prentice Hall Kinds of Mutations Translocations occurs when part of one chromosome breaks off and attaches to another.

90 Copyright Pearson Prentice Hall Significance of Mutations Many mutations have little or no effect on gene expression. Some mutations are the cause of genetic disorders. Polyploidy is the condition in which an organism has extra sets of chromosomes.

91 Copyright Pearson Prentice Hall 12–4 A mutation in which all or part of a chromosome is lost is called a(an) a.duplication. b.deletion. c.inversion. d.point mutation.

92 Copyright Pearson Prentice Hall 12–4 A mutation that affects every amino acid following an insertion or deletion is called a(an) a.frameshift mutation. b.point mutation. c.chromosomal mutation. d.inversion.

93 Copyright Pearson Prentice Hall 12–4 A mutation in which a segment of a chromosome is repeated is called a(an) a.deletion. b.inversion. c.duplication. d.point mutation.

94 Copyright Pearson Prentice Hall 12–4 The type of point mutation that usually affects only a single amino acid is called a.a deletion. b.a frameshift mutation. c.an insertion. d.a substitution.

95 Copyright Pearson Prentice Hall 12–4 When two different chromosomes exchange some of their material, the mutation is called a(an) a.inversion. b.deletion. c.substitution. d.translocation.

96 Copyright Pearson Prentice Hall 12-5 Gene Regulation Fruit fly chromosome Fruit fly embryo Adult fruit fly Mouse chromosomes Mouse embryo Adult mouse

97 Copyright Pearson Prentice Hall Gene Regulation: An Example a.E. coli provides an example of how gene expression can be regulated. b.An operon is a group of genes that operate together. c.In E. coli, these genes must be turned on so the bacterium can use lactose as food. d.Therefore, they are called the lac operon.

98 Copyright Pearson Prentice Hall Gene Regulation: An Example –How are lac genes turned off and on?

99 Copyright Pearson Prentice Hall Gene Regulation: An Example –The lac genes are turned off by repressors and turned on by the presence of lactose.

100 Copyright Pearson Prentice Hall Gene Regulation: An Example –On one side of the operon's three genes are two regulatory regions. a.In the promoter (P) region, RNA polymerase binds and then begins transcription.

101 Copyright Pearson Prentice Hall Gene Regulation: An Example a.The other region is the operator (O).

102 Copyright Pearson Prentice Hall Gene Regulation: An Example –When the lac repressor binds to the O region, transcription is not possible.

103 Copyright Pearson Prentice Hall Gene Regulation: An Example When lactose is added, sugar binds to the repressor proteins.

104 Copyright Pearson Prentice Hall Gene Regulation: An Example The repressor protein changes shape and falls off the operator and transcription is made possible.

105 Copyright Pearson Prentice Hall Gene Regulation: An Example Many genes are regulated by repressor proteins. Some genes use proteins that speed transcription. Sometimes regulation occurs at the level of protein synthesis.

106 Copyright Pearson Prentice Hall Eukaryotic Gene Regulation –How are most eukaryotic genes controlled?

107 Copyright Pearson Prentice Hall Eukaryotic Gene Regulation –Operons are generally not found in eukaryotes. –Most eukaryotic genes are controlled individually and have regulatory sequences that are much more complex than those of the lac operon.

108 Copyright Pearson Prentice Hall Eukaryotic Gene Regulation Many eukaryotic genes have a sequence called the TATA box. Promoter sequences Upstream enhancer TATA box Introns Exons Direction of transcription

109 Copyright Pearson Prentice Hall Eukaryotic Gene Regulation The TATA box seems to help position RNA polymerase. Promoter sequences Upstream enhancer TATA box Introns Exons Direction of transcription

110 Copyright Pearson Prentice Hall Eukaryotic Gene Regulation Eukaryotic promoters are usually found just before the TATA box, and consist of short DNA sequences. Promoter sequences Upstream enhancer TATA box Introns Exons Direction of transcription

111 Copyright Pearson Prentice Hall Eukaryotic Gene Regulation Genes are regulated in a variety of ways by enhancer sequences. Many proteins can bind to different enhancer sequences. Some DNA-binding proteins enhance transcription by: a.opening up tightly packed chromatin b.helping to attract RNA polymerase c.blocking access to genes.

112 Copyright Pearson Prentice Hall Development and Differentiation a.As cells grow and divide, they undergo differentiation, meaning they become specialized in structure and function. b.Hox genes control the differentiation of cells and tissues in the embryo.

113 Copyright Pearson Prentice Hall Development and Differentiation Careful control of expression in hox genes is essential for normal development. All hox genes are descended from the genes of common ancestors.

114 Copyright Pearson Prentice Hall Development and Differentiation Hox Genes Fruit fly chromosome Fruit fly embryo Adult fruit fly Mouse chromosomes Mouse embryo Adult mouse

115 Copyright Pearson Prentice Hall 12–5 –Which sequence shows the typical organization of a single gene site on a DNA strand? a.start codon, regulatory site, promoter, stop codon b.regulatory site, promoter, start codon, stop codon c.start codon, promoter, regulatory site, stop codon d.promoter, regulatory site, start codon, stop codon

116 Copyright Pearson Prentice Hall 12–5 –A group of genes that operates together is a(an) a.promoter. b.operon. c.operator. d.intron.

117 Copyright Pearson Prentice Hall 12–5 –Repressors function to a.turn genes off. b.produce lactose. c.turn genes on. d.slow cell division.

118 Copyright Pearson Prentice Hall 12–5 –Which of the following is unique to the regulation of eukaryotic genes? a.promoter sequences b.TATA box c.different start codons d.regulatory proteins

119 Copyright Pearson Prentice Hall 12–5 –Organs and tissues that develop in various parts of embryos are controlled by a.regulation sites. b.RNA polymerase. c.hox genes. d.DNA polymerase.


Download ppt "Copyright Pearson Prentice Hall 12–1 DNA. Copyright Pearson Prentice Hall Griffith and Transformation In 1928, British scientist Fredrick Griffith was."

Similar presentations


Ads by Google