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Albia Dugger Miami Dade College Cecie Starr Christine Evers Lisa Starr www.cengage.com/biology/starr Chapter 8 DNA Structure and Function (Sections 8.1.

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Presentation on theme: "Albia Dugger Miami Dade College Cecie Starr Christine Evers Lisa Starr www.cengage.com/biology/starr Chapter 8 DNA Structure and Function (Sections 8.1."— Presentation transcript:

1 Albia Dugger Miami Dade College Cecie Starr Christine Evers Lisa Starr Chapter 8 DNA Structure and Function (Sections )

2 8.1 A Hero Dog’s Golden Clones Making clones of adult animals is a common practice that continues to raise serious ethical questions Cloning techniques are not perfect; many attempts are required to produce a clone, and clones often have health problems clone Genetically identical copy of an organism

3 A Hero Dog Canadian police officer James Symington’s search-and-rescue dog Trakr led rescuers to the fifth and final survivor of the World Trade Center attacks

4 Trakr’s Golden Clones Trakr died of a degenerative disease probably linked to toxic smoke at Ground Zero – but his DNA lives on in his clones Trakr won the Golden Clone Giveaway, a contest to find the world’s most clone-worthy dog Trakr’s DNA was shipped to Korea, inserted into dog eggs, and implanted into surrogate mother dogs

5 Clone Puppies Trakr’s clones were delivered to Symington in July 2009

6 8.2 Eukaryotic Chromosomes All organisms pass DNA to offspring when they reproduce In cells, each DNA molecule is organized as a chromosome chromosome Structure consisting of DNA and associated proteins Carries part or all of a cell’s genetic information Eukaryotic cells have a number of chromosomes

7 Chromosome Duplication During most of a cell’s life, each of its chromosomes consists of one DNA molecule As it prepares to divide, the cell duplicates its chromosomes, so both offspring get a full set After chromosomes are duplicated, each consists of two DNA molecules (sister chromatids) attached to each other at a centromere

8 Key Terms sister chromatid One of two attached members of a duplicated eukaryotic chromosome centromere Constricted region in a eukaryotic chromosome where sister chromatids are attached

9 Chromosome Duplication

10 p. 124 a chromosome (duplicated) its sister chromatid centromere a chromosome (unduplicated) one chromatid Chromosome Duplication

11 Sister Chromatids A duplicated chromosome consists of two long, tangled filaments (sister chromatids) bunched into an X shape

12 Chromosome Structure 1.DNA in a nucleus is divided into chromosomes 2.At its most condensed, a duplicated chromosome is packed tightly into an X shape 3.A chromosome unravels as a single fiber – a hollow cylinder formed by coiled coils 4.The coiled coils consist of a long molecule of DNA and associated proteins 5.The DNA molecule wraps around a core of histone proteins, forming “beads” called nucleosomes 6.The DNA molecule has two strands twisted in a double helix

13 Key Terms histone Type of protein that structurally organizes eukaryotic chromosomes nucleosome A length of DNA wound around a spool of histone proteins

14 Fig 8.2a, p. 124 The DNA molecule itself has two strands that are twisted into a double helix. The DNA inside the nucleus of a eukaryotic cell is typically divided up into a number of chromosomes. Inset: a duplicated human chromosome. At its most condensed, a duplicated chromosome is packed tightly into an X shape. A chromosome unravels as a single fiber, a hollow cylinder formed by coiled coils. The coiled coils consist of a long molecule of DNA (blue) and the proteins that are associated with it (purple). At regular intervals, the DNA molecule is wrapped twice around a core of histone proteins. In this “beads-on-a-string” structure, the “string” is the DNA, and each “bead” is called a nucleosome Chromosome Structure

15 ANIMATION: Chromosome structural organization To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

16 Chromosome Number Eukaryotic DNA is divided among a number of chromosomes that differ in length and shape The sum of all chromosomes in a cell of a given type is the chromosome number Diploid cells have two of each type of chromosome Each species has a characteristic chromosome number

17 Key Terms chromosome number Sum of all chromosomes in a cell of a given type diploid Having two of each type of chromosome characteristic of the species (2n)

18 Human Chromosome Number Human body cells have 46 chromosomes (chromosome number 46) Human body cells have two of each type of chromosome (23 pairs) so the chromosome number is diploid (2n) Each pair of chromosomes has two versions, one maternal and one paternal

19 Types of Chromosomes Members of a pair of sex chromosomes differ among males and females – the differences determine an individual’s sex All others chromosomes are autosomes, which are the same in both females and males Autosomes of a pair have the same length, shape, and centromere location, and carry the same genes

20 Key Terms sex chromosome Member of a pair of chromosomes that differs between males (XY) and females (XX) autosome Any chromosome other than a sex chromosome The two members of each pair have the same length and shape, and hold information about the same traits

21 Karyotype A karyotype can reveal abnormalities in an individual’s complement of chromosomes A micrograph of a single cell is digitally rearranged so images of chromosomes are lined up by centromere location, and arranged according to size, shape, and length karyotype Image of an individual’s complement of chromosomes arranged by size, length, shape, and centromere location

22 A Human Karyotype 22 pairs of autosomes and 2 X chromosomes

23 ANIMATION: Karyotype preparation To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

24 Sex Determination in Humans Body cells of human females contain two X chromosomes (XX); those of males contain one X and one Y (XY) New individuals randomly inherit one sex chromosome from the mother and one from the father All female eggs have one X chromosome Male sperm have either an X or a Y (50-50 chance) If an X-bearing sperm fertilizes an X-bearing egg, the resulting individual will be female – if the sperm carries a Y chromosome, the individual will develop into a male

25 Sex Determination in Humans

26 Fig 8.4, p. 125 diploid reproductive cell in male sperm union of sperm and egg at fertilization diploid reproductive cell in female eggs Sex Determination in Humans

27 Fig 8.4, p. 125 diploid reproductive cell in male diploid reproductive cell in female spermeggs union of sperm and egg at fertilization XX XY Stepped Art Sex Determination in Humans

28 ANIMATION: Human sex determination To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

29 Key Concepts Chromosomes DNA of a eukaryotic cell is divided among a characteristic number of chromosomes that differ in length and shape Sex chromosomes determine an individual’s gender Proteins associated with eukaryotic DNA help organize chromosomes so they can pack into a nucleus

30 8.3 Discovery of DNA’s Function Almost one hundred years of experiments with bacteria and bacteriophage offer solid evidence that deoxyribonucleic acid (DNA), not protein, is the hereditary material of life

31 Early and Puzzling Clues Late 1800s: Johannes Miescher found that nuclei contain an acidic substance composed mostly of nitrogen and phosphorus Later, that substance would be called deoxyribonucleic acid (DNA) Early 1900s: Frederick Griffith used two strains of Streptococcus pneumoniae in a series of experiments that revealed a clue about inheritance

32 Griffith’s Experiments Griffith isolated two strains (types) of Streptococcus pneumoniae, a bacteria that causes pneumonia: harmless, rough (R) and killer, smooth (S) The hereditary material of harmful Streptococcus pneumoniae cells was transferred from dead S cells into live R cells – transforming harmless cells (R) into killers (S) The transformation was permanent and heritable

33 Griffith’s Experiments 1. Mice injected with live cells of harmless strain R do not die Live R cells in blood 2. Mice injected with live cells of strain S die Live S cells in blood

34 Griffith’s Experiments (cont.) 3. Mice injected with heat- killed S cells do not die No live S cells in blood 4. Mice injected with live R cells plus heat-killed S cells die Live S cells in blood

35 Fig 8.5, p. 126 Mice injected with live R cells plus heat-killed S cells die. Live S cells in their blood. Mice injected with live cells of harmless strain R do not die. Live R cells in their blood. Mice injected with live cells of killer strain S die. Live S cells in their blood. Mice injected with heat-killed S cells do not die. No live S cells in their blood Griffith’s Experiments

36 ANIMATION: Griffith's experiment To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

37 More Clues 1940s: Oswald Avery and Maclyn McCarty tried to identify Griffiths “transforming principle” Separated lipid, protein, and nucleic acid components of S cells S cell extract still transformed R cells after treatment with lipid- and protein-destroying enzymes, so transforming principle must be nucleic acid (RNA or DNA) S cell extract still transformed R cells after treatment with RNA-degrading enzymes, but not after treatment with DNA-degrading enzymes, so DNA had to be the transforming principle

38 Confirmation of DNA’s Function Alfred Hershey and Martha Chase tested whether genetic material injected by bacteriophages into bacteria is DNA, protein, or both Based on the fact that proteins contain more sulfur than phosphorus, and DNA contains more phosphorus than sulfur bacteriophage Virus that infects bacteria

39 Bacteriophages Top, model of a bacteriophage Bottom, micrograph of three viruses injecting DNA into an E. coli cell

40 Fig 8.6a.1, p. 127 DNA inside protein coat tail fiber hollow sheath Bacteriophages

41 Fig 8.6a.2, p. 127 Bacteriophages

42 Hershey–Chase Experiment 1. Bacteria were infected with virus particles that had proteins labeled with a radioisotope of sulfur ( 35 S) Viruses were dislodged from the bacteria by whirling the mixture in a kitchen blender Most radioactive sulfur was detected in viruses, not in bacterial cells Viruses had not injected protein into the bacteria

43 Hershey–Chase Experiment 1

44 Fig 8.6b, p. 127 B In one experiment, bacteria were infected with virus particles that had been labeled with a radioisotope of sulfur ( 35 S). The sulfur had labeled only viral proteins. The viruses were dislodged from the bacteria by whirling the mixture in a kitchen blender. Most of the radioactive sulfur was detected in the viruses, not in the bacterial cells. The viruses had not injected protein into the bacteria. DNA being injected into bacterium Virus particle coat proteins labeled with 35 S 35 S remains outside cells Hershey–Chase Experiment 1

45 Hershey–Chase Experiment 2 Bacteria were infected with virus particles that had DNA labeled with a radioisotope of phosphorus ( 32 P) When viruses were dislodged from the bacteria, radioactive phosphorus was detected mainly inside the bacterial cells Viruses had injected DNA into the cells—evidence that DNA is the genetic material of this virus

46 Hershey–Chase Experiment 2

47 Fig 8.6c, p. 127 C In another experiment, bacteria were infected with virus particles that had been labeled with a radioisotope of phosphorus ( 32 P). The phosphorus had labeled only viral DNA. When the viruses were dislodged from the bacteria, the radioactive phosphorus was detected mainly inside the bacterial cells. The viruses had injected DNA into the cells—evidence that DNA is the genetic material of this virus. Labeled DNA being injected into bacterium Virus DNA labeled with 32 P 32 P remains inside cells Hershey–Chase Experiment 2

48 DNA being injected into bacterium Virus particle coat proteins labeled with 35 S 35 S remains outside cells Fig 8.6, p. 127 Stepped Art Labeled DNA being injected into bacterium Virus DNA labeled with 32 P 32 P remains inside cells Hershey–Chase Experiment 2

49 ANIMATION: Hershey-Chase experiments To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

50 Key Concepts Discovery of DNA’s Function The work of many scientists over more than a century led to the discovery that DNA is the molecule that stores hereditary information


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