Deoxyribonucleic acid DNA Nucleic Acid Polymer monomer nucleotide
• Deoxyribonucleic acid (DNA) • Nucleic Acid – • Polymer monomer = nucleotide – 2 kinds of nucleic acids: DNA and RNA.
Coding sections in DNA are called genes Genes code for protein production; (the hereditary info. in DNA tells cells how to make proteins)
• Nucleotide: three components (CP: 230) (H: 197) – 5 C sugar (deoxyribose) – phosphate group – nitrogenous base (4 kinds in DNA) • Thymine • Adenine • Guanine • Cytosine
• Nucleotide: three components (CP: 230) (Hon: 197) – 5 C sugar – phosphate group – nitrogenous base (4 kinds in DNA)
Four Kinds of Nitrogenous Bases • Adenine binds to Thymine N C OC O N CC • Cytosine binds to Guanine N C C C N C Cytosine O N C C O C N C Thymine N N C C N N C Adenine N C Guanine N C • A-T and C-G (always)
DNA STRUCTURE • Shape is like twisted ladder. • Called a double helix -two twisted strands – Bases =rungs of a ladder • hydrogen bonds hold pairs together; A-T, C-G – Sugars - phosphates form sides of ladder. • Covalent bonds in backbone
Carbons in the sugar are labeled 1’ (one prime) to 5’.
Model parts: • • 12 – White Tees [Deoxyribose] 6 – White connectors [Hydrogen bond] 12 – Black [Phosphate group] 3 – Green [Guanine] 3 – Blue [Adenine] 3 – Red [Thymine] 3 – Yellow [Cytosine]
DNA Animation http: //www. johnkyrk. com/DNAanatomy. html
Packaging DNA Fundamental unit is Nucleosome – • DNA wound around proteins called histones. • (Hon. page 151) • Occurs at Prophase
Nucleosome
Nucleosomes • Lowest DNA packaging level • thread wound around a spool
DNA - By The Numbers! • Each cell has about 2 meters (6 ft) of DNA. • The average human has 60 -75 trillion cells. • Avg human has enough DNA to go from the Earth to the sun more than 400 times. • DNA has a diameter of The earth is 150 billion meters only 0. 000002 or 93 million miles from meters (20Ǻ) the sun. [1Ǻ =10 -10 m]
Karyotypes • Normal human male karyotype (the total set of chrom. of an organism)
Karyotypes • Normal human female karyotype
The History of DNA • Gregor Mendel-1866 – Determined “Unit characters” were the method of passing on traits for inheritance • Friedrich Meischer - 1868 – Studied nuclei of pus cells obtained from discarded surgical bandages – Detected a phosphorus-containing substance that he named nuclein.
• Frederick Griffith 1928 : Work with Bacteria – Found that DNA taken from a virulent (disease-causing) strain of bacteria (Streptococcus pneumoniae) – Transformed a non-virulent form of the bacterium into a virulent form.
Oswald Avery, Colin Mac. Leod, and Maclyn Mc. Carty 1943 Continued the study of “Transformation” principle
Mendel Avery Meischer Griffith Mac. Leod Mc. Carty
Transformation Of Bacteria Two Strains Of Streptococcus Capsule Rough Strain (Harmless) Smooth Strain w/Capsule (Virulent)
Transformation Of Bacteria -Griffith’s Experiment Smooth (virulent) OUCH! Control Rough Control Experimental
The History of DNA • Alfred Hershey and Martha Chase - 1952 – radioactive isotope tracer experiment – bacterial virus (bacteriophage T 2) infects a host cell ( bacterium Escherichia coli) – found that T 2 virus DNA, not its protein coat, enters the host cell – genetic information for replication of the virus
T 2 grown in media containing S 35 incorporate S 35 into their proteins Using S 35 T 2 attach to bacteria and inject genetic material Bacteria grown in normal nonradioactive media When centrifuged, phage protein coats remain in the supernatant while bacteria form a pellet. The supernatant is radioactive, but the pellet is not. Did protein enter the bacteria? Blending causes phage protein coat to fall off Is protein the genetic material?
P 32 T 2 grown in containing media incorporate P 32 into their DNA Using P 32 Bacteria grown T 2 attach to bacteria and inject genetic material in normal nonradioactive media When centrifuged, phage protein coats remain in the supernatant while bacteria form a pellet The pellet is radioactive, but the supernatant is not. Did DNA enter the bacteria? Blending causes phage protein coat to fall off Is DNA the genetic material?
The History of DNA Structure • Erwin Chargaff- 1940 - “Chargaff’s rule” – four bases may occur in varying proportions in DNA of different organisms – # of A = # of T, w/ two hydrogen bonds – = # of G and C are present w/ 3 hydrogen bonds • Rosalind Franklin and Maurice Wilkins – X-ray diffraction study concluded DNA fibers have two strands.
The History of DNA Structure James Watson and Francis Crick University of Cambridge -1953 Worked on problem of making a DNA molecule model that was double stranded but also had the specific A - T and G - C base equivalencies Solution-double helical structure for DNA.
Franklin Chargaff Wilkins
Watson and Crick
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