Mr. Hunter Biology 02/04/2013• Objective(s)• SWBAT• Identify various experiments involving the discovery of DNA.• Analyze the structure of DNA in terms of nucleotides, base pair rules and hydrogen bonding.• Bell Ringer – What is the complementary (matching) base sequence of the following strand of DNA: GGGCATACCGGAT - Original strand CCCGTATGGCCTA - Complementary strand
A. Is the structure of DNA the same for all the organisms in the pictures on the left?B. Why don’t you look like a spider or an elephant? – Explain Answer: DNA has general similar Answer molecular structure. The arrangement of the monomer units (nucleotides) are different for each organism.
• Maury Polvich – Paternity TestingThe Popularity of DNA and beyond • CSI – Forensic action series • Forensic Files- Case studies of crimes using the latest molecular biology techniques (DNA)
DNA: Experimentation and Discovery Mr. Hunter Biology Chapter 10 02/04/2013mrhunterspage.blogspot.com Kennedy High School
• Fredrick Griffith conductedExperimental Discovery experiments in 1928 to try to find a cure for pneumonia. • He accidently found that one of the two strains of bacteria that he was studying was able to transform the nonvirulent ( not causing disease). form into a virulent form (causing disease) • He concluded that a hereditary factor was released which caused the transformation • Question: What two forms of bacteria did Griffith use in his experiment?
• In the early 1940s, AmericanExperimental Discovery Scientist, Oswald Avery wanted to test the results of Griffith’s transformation experiment. • Wanted to determine if transforming agent was proteins, RNA or DNA • Determined using enzymes that destroyed RNA, proteins and DNA. Found that DNA was responsible for the transformation of the harmless strain into the deadly strain. • Question: What were the three macromolecules tested in Avery’s experiment?
• In 1928, Alfred Hershey andExperimental Discovery Martha Chase wanted to know if proteins or DNA was passed from viruses to bacterial cells (E-coli) • Bacteriophages are viruses that infect bacteria. • Radioactive Sulfur was used to label the protein coat of the virus. Radioactive Phosphorus was used to label the DNA of the virus. • They found that DNA was incorporated in the cells infected by the virus. • Question: Why were sulfur and Phosphorus used in their experiments?
1. Briefly describe the experiments ofREVIEW Griffith, Avery and Hershey / Chase 2. What are the monomer units of DNA known as _________ 3. Griffith used heat to kill the virulent strain of bacteria in his experiment. The hereditary information was still passed on. What can you can conclude about the stability of DNA and proteins in terms of temperature? 4. Compare / Contrast the experiments of Griffith and Avery 5. What is a bacteriophage? * You may use one of the above review questions as an exit question for today. 02/04/13
• Watson and Crick wereExperimental Discovery scientists in the early 1950s who determined the double helix structure of DNA. • Series of sugar phosphates and nitrogen bases are the components of a nucleotide. Pg. 197 text fig. 10-6
DNA• Deoxyribonucleic acid (DNA)• Made of two long chains of repeating subunits called nucleotides• The long chains are coiled to form a double helix
The Structure of • By the 1950s most scientists DNA were convinced that genes were made of DNA (basic functional structure of genetic material deoxyribonucleic acid) • Watson and Crick discovered the double helix structure of DNA • Each strand of the double helix is made of nucleotides • Nucleotides are the subunits of DNA
DNA has a double helixstructure• DNA was discoveredto have a double helixStructure• The structure is heldin place by HydrogenBonds joiningnucleotide bases.•There are (2) H-bondsbetween the bases Aand T. There are (3) H-bonds between thebases G and C
Nucleotides • The 5 carbon sugar in the nucleotide molecule of DNA isContinued called deoxyribose • Sugar molecules and phosphate groups are the same for nucleotide molecules in DNA • The nitrogen bases may be of 4 different kinds • 2 Double Ring Purine bases: • 2 Single Ring Pyrimidine bases
Nitrogen Bases• Purines (Double Rings)• 1. Adenine (A)• 2. Guanine (G)• Pyrimidines (Single Rings)• 1. Thymine (T)• 2. Cytosine (C)• Erwin Chargaff Rules of Base Pairing : A = T, C = G• The % of A =T and % of G = C
Replication of DNA• DNA is copied with the help of many enzymes• Complementary structure of DNA is used to make copies of the DNA when the cell divides• Watson and Crick proposed that one strand of DNA serves as a template (pattern) on which the other strand is built• The process of making a copy of DNA is called DNA Replication
Steps of Replication• 1. The enzyme Helicase separates the double helix by breaking Hydrogen bonds between the bases AT and CG. Other proteins hold the strands apart so they won’t twist back together.• The points at which the strands separate are called replication forks.• 2. The enzyme, DNA polymerase travels along the strands of DNA adding new nucleotides
• 3. DNA polymerase remains attached until all of the DNA has been copied.• This process produces 2 DNA molecules composed of an old and new strand• The nucleotide sequences of both of the DNA molecules are identical
Review1. What do the initials DNA stand for ________________2. Name the two scientists responsible for the discovery of the double helix structure of DNA___________________3. Define Nucleotide_____________________________4. List the three parts of a nucleotide.5. Name the two groups of nitrogen bases in DNA (P)_______ and (P) ________6. The ________ have a double chemical ring structure and the _______ have a single chemical ring structure.7. The four types of nitrogen bases found in DNA are:8. The two bases that belong to the group of Purines are _________ and _______. The two bases that belong to the Pyrimidines are ________ and __________.9. What bases complement (match) the following DNA strand : AATTGCCGA
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