Mr. HunterBiology 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 RingerBell Ringer – What is the complementary (matching)

base sequence of the following strand of DNA: GGGCATACCGGAT - Original strand

CCCGTATGGCCTA - Complementary strand

A.A. Is the structure of DNA the Is the structure of DNA the same forsame for all all the organisms in the organisms in the pictures on the left? the pictures on the left?

B.B. Why don’t you look like a Why don’t you look like a spider or an elephant? – spider or an elephant? – ExplainExplain

AnswerAnswer: DNA has general similar DNA has general similar molecular structure. The arrangement molecular structure. The arrangement of the monomer units (nucleotides) are of the monomer units (nucleotides) are different for each organism.different for each organism.

The Popularity of DNAThe Popularity of DNA

• Maury Polvich Maury Polvich – Paternity Testing – Paternity Testing and beyondand beyond

• CSI CSI – Forensic action series– Forensic action series• Forensic Files- Forensic Files- Case studies of crimes Case studies of crimes

using the latest molecular biology using the latest molecular biology techniques (DNA)techniques (DNA)

DNA: DNA: Experimentation Experimentation and and DiscoveryDiscovery

Mr. HunterBiology Chapter 10

02/04/2013mrhunterspage.blogspot.com

Kennedy High School

Experimental DiscoveryExperimental Discovery

• Fredrick Griffith Fredrick Griffith conducted conducted experiments in 1928 to try to experiments in 1928 to try to find a cure for pneumonia.find a cure for pneumonia.

• He accidently found that one of He accidently found that one of the two strains of bacteria that the two strains of bacteria that he was studying was able tohe was studying was able to transform transform the the nonvirulentnonvirulent ( not ( not causing disease). form into a causing disease). form into a virulentvirulent form (causing disease)form (causing disease)

• He concluded that a He concluded that a hereditaryhereditary factor was released which factor was released which caused the caused the transformationtransformation

• QuestionQuestion: : What two forms of What two forms of bacteria did Griffith use in his bacteria did Griffith use in his experiment?experiment?

Experimental DiscoveryExperimental Discovery

• In the early 1940s, American In the early 1940s, American Scientist, Scientist, Oswald Avery Oswald Avery wanted wanted to test the results of Griffith’s to test the results of Griffith’s transformation experiment.transformation experiment.

• Wanted to determine if Wanted to determine if transforming agent was transforming agent was proteinsproteins, , RNA RNA or or DNADNA

• Determined using Determined using enzymesenzymes that that destroyed RNA, proteins and destroyed RNA, proteins and DNA. Found that DNA. Found that DNA was DNA was responsible for the responsible for the transformation of the harmless transformation of the harmless strain into the deadly strain.strain into the deadly strain.

• QuestionQuestion: : What were the three What were the three macromolecules tested in Avery’s macromolecules tested in Avery’s experiment?experiment?

Experimental DiscoveryExperimental Discovery

• In 1928, In 1928, Alfred Hershey Alfred Hershey and and Martha Chase Martha Chase wanted to know if wanted to know if proteins or DNA was passed from proteins or DNA was passed from viruses to bacterial cells (E-coli)viruses to bacterial cells (E-coli)

• Bacteriophages Bacteriophages are viruses that are viruses that infect bacteria.infect bacteria.

• Radioactive Radioactive SulfurSulfur was used to was used to label the label the protein coat protein coat of the virus. of the virus. Radioactive Radioactive PhosphorusPhosphorus was used was used to label theto label the DNA DNA of the virus.of the virus.

• They found that DNA was They found that DNA was incorporated in the cells infected incorporated in the cells infected by the virus.by the virus.

• QuestionQuestion: : Why were sulfur and Why were sulfur and Phosphorus used in their Phosphorus used in their experiments?experiments?

REVIEW

1.1. Briefly describe the experiments of Briefly describe the experiments of Griffith, Avery and Hershey / ChaseGriffith, Avery and Hershey / Chase

2.2. What are the monomer units of What are the monomer units of DNA known as _________DNA known as _________

3.3. Griffith used heat to kill the Griffith used heat to kill the virulent strain of bacteria in his virulent strain of bacteria in his experiment. The hereditary experiment. The hereditary information was still passed on. information was still passed on. What can you can conclude about What can you can conclude about the stability of DNA and proteins in the stability of DNA and proteins in terms of temperature?terms of temperature?

4.4. Compare / Contrast the Compare / Contrast the experiments of Griffith and Averyexperiments of Griffith and Avery

5.5. What is a bacteriophage?What is a bacteriophage?

* * You may use one of the above review You may use one of the above review questions as an exit question for questions as an exit question for today. 02/04/13today. 02/04/13

Experimental DiscoveryExperimental Discovery• Watson and Crick Watson and Crick were were

scientists in the early 1950s scientists in the early 1950s who determined the double who determined the double helix structure of DNA.helix structure of DNA.

• Series of sugar phosphates and Series of sugar phosphates and nitrogen bases are the nitrogen bases are the components of acomponents of a nucleotide nucleotide. . Pg. 197 text fig. 10-6Pg. 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 The Structure of DNA DNA

• By the 1950s most scientists By the 1950s most scientists were convinced that genes were convinced that genes were made of DNA (basic were made of DNA (basic functional structure of genetic functional structure of genetic material deoxyribonucleic acid)material deoxyribonucleic acid)

• Watson and CrickWatson and Crick discovered discovered the double helix structure of the double helix structure of DNADNA

• Each strand of the double helix Each strand of the double helix is made of is made of nucleotidesnucleotides

• Nucleotides are the subunits of Nucleotides are the subunits of DNADNA

DNA has a double helix structure

• DNA was discovered to have a double helix Structure • The structure is held in place by Hydrogen Bonds joining nucleotide bases.•There are (2) H-bonds between the bases A and T. There are (3) H-bonds between the bases G and C

NucleotideNucleotideThree Parts:Three Parts:1.1.Phosphate GroupPhosphate Group2.2.Five Carbon Sugar Five Carbon Sugar MoleculeMolecule3.3.Nitrogen Containing Nitrogen Containing BaseBase

Nucleotides Continued

• The 5The 5 carbon sugar in the carbon sugar in the nucleotide molecule of DNA is nucleotide molecule of DNA is called deoxyribosecalled deoxyribose

• Sugar molecules and Sugar molecules and phosphate groups are the same phosphate groups are the same for nucleotide molecules in for nucleotide molecules in DNADNA

• The nitrogen bases may be of 4 The nitrogen bases may be of 4 different kindsdifferent kinds

• 2 Double Ring Purine bases: 2 Double Ring Purine bases: • 2 Single Ring Pyrimidine bases2 Single Ring Pyrimidine bases

Nitrogen BasesNitrogen Bases• Purines (Double Rings)Purines (Double Rings)• 1. Adenine (A)1. Adenine (A)• 2. Guanine (G)2. Guanine (G)

• Pyrimidines (Single Rings)Pyrimidines (Single Rings)• 1.1. Thymine (T)Thymine (T)• 2.2. Cytosine (C)Cytosine (C)

• Erwin Chargaff Rules of BaseErwin Chargaff Rules of Base PairingPairing : A = T, C = G : A = T, C = G

• The % of A =T and % of G = CThe % of A =T and % of G = C

Replication of DNAReplication of DNA

• DNA is copied with the help of many enzymesDNA is copied with the help of many enzymes• Complementary structure of DNA is used to Complementary structure of DNA is used to

make copies of the DNA when the cell dividesmake copies of the DNA when the cell divides• Watson and Crick proposed that one strand of Watson and Crick proposed that one strand of

DNA serves as a template (pattern) on which DNA serves as a template (pattern) on which the other strand is builtthe other strand is built

• The process of making a copy of DNA is called The process of making a copy of DNA is called DNA ReplicationDNA Replication

Steps of ReplicationSteps of Replication

• 1. The enzyme1. The enzyme HelicaseHelicase separates the double separates the double helix by helix by breaking Hydrogen bondsbreaking Hydrogen bonds between between the bases the bases ATAT and and CGCG. . Other Other proteinsproteins hold the hold the strands apart so they won’t twist back strands apart so they won’t twist back together.together.

• The points at which the strands separate are The points at which the strands separate are called called replication forksreplication forks..

• 2. The enzyme, 2. The enzyme, DNA polymerase DNA polymerase travels along travels along the strands of DNA adding the strands of DNA adding new nucleotidesnew nucleotides

• 3. 3. DNA polymerase DNA polymerase remains attached until all remains attached until all of the DNA has been copied. of the DNA has been copied.

• This process produces This process produces 2 DNA molecules 2 DNA molecules composed of an old and new strandcomposed of an old and new strand

• The The nucleotide sequences nucleotide sequences of both of the DNA of both of the DNA molecules are molecules are identical identical

Review 1. 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