FINDING DNA

Proof of DNA as Genetic Material

• Was the genetic material protein or DNA?

• Mendel (peas) and Morgan (flies) did not know it was DNA. Worksheet links

• Bozeman Biology: DNA and RNA Part I Bozeman Biology: DNA and RNA Part II

Frederick Griffith

• A medical officer was trying to find a vaccine against pneumococcus

Rough and Smooth Pneumococcus

Griffith 1920’s

• Streptococcus pneumoniae used to show a “transforming factor”

Griffith’s Conclusion

• Some material in the heat-killed S strain that was responsible for “transforming” the R-strain into a lethal form

• transformation = passing the inheritance factor from one organism to another

• THIS TRANSFORMING FACTOR WAS LATER FOUND TO BE DNA

Oswald Avery 1944

He had reported that DNA, not protein (which was believed at the time), was the hereditary substance (transforming material).

Studied medical research

Oswald Avery 1940’s

Avery’s Conclusion

• Removed DNA, RNA, protein from S-strain pneumococcus

• AVERY PROVED THAT DNA WAS THE TRANSFORMING MATERIAL

Alfred Hershey and Margaret Chase 1953

• Showed that the hereditary material in bacteriophage viruses is DNA.

DNA in water

Hershey-Chase

• Hershey-Chase Bacteriophages Youtube• McGraw-Hill Hershey-Chase Experiment

Radioactive P32 in DNARadioactive S35 in protein

Hershey-Chase

• CONCLUSION –

• DNA is genetic material because (32P) nucleic acid not (35S) protein guides viral replication

Bacteriophages (“bacteria-eaters”)

Mostly made of just protein coat and DNA

Virus Examples

• Cold Virus HIV Virus

Bird Flu Virus

Ebola Virus

Herpes Virus

Bacteriophage Structure

Virus: Are they Alive?

• Viruses can only replicate in a living host.

• "Viruses straddle the definition of life. They lie somewhere between supra molecular complexes and very simple biological entities. Viruses contain some of the structures and exhibit some of the activities that are common to organic life, but they are missing many of the others.”

• Dr. Mark Young of MSU youtube (4:00)

Bacteriophage Lytic Infection

1.Attach to host

2. Insert DNA

3. Make and assemble DNA parts

4. Lyse (burst)

EXAMPLES:ColdFlu

Lysogenic Infection

• BIOL 230 Lecture Guide - Lysogenic Life Cycle of a Temperate Bacteriophage (animation link)

• 1. Virus lands on host.• 2. Virus injects DNA into host.• 3. Virus DNA attaches to host DNA =

prophage.• 4. Virus Prophage will become lytic when

conditions are favorable (you are sick, tired).

Lysogenic Cycle Animation

• Animation Quiz 2 - Lamda Phage Replication Cycle

• EXAMPLES:HERPESHIV

• CHICKEN POX

Click on “Journey into DNA”

• NOVA Online | Cracking the Code of Life | Journey into DNA (keep clicking on “zoom” + button)

• View for extra credit • Write 10 things you

learned about DNA

What is the structure of DNA?

• It is a nucleic acid• Polynucleotide =

Made of long chains of Nucleotides

DNA Nucleotide

OO=P-O O

Phosphate Group

NNitrogenous base (A, G, C, or T)

CH2

O

C1C4

C3 C2

5

Sugar(deoxyribose)

DNA Structure

• NUCLEOTIDE• POLYNUCLEOTIDE

A Nucleotide

• MADE OF:–Sugar–Phosphate–Base

• Deoxyribose sugar• PO4

• 4 kinds:• (A) (G) (T) (C)(names on next slide)

4 Types of Base Pairs

• A = adenine• T = thymine• C = cytosine• G = guanine• NOW SING THE DNA SONG

Nitrogenous Bases

• PURINES -2 rings

1. Adenine (A)

2. Guanine (G)

• PYRIMIDINES -1 ring

3. Thymine (T)

4. Cytosine (C) T or C

A or G

DNA

•Deoxyribonucleic Acid

• (Get out colored pencils)

DNA Double Helix

NitrogenousBase (A,T,G or C)

“Rungs of ladder”

“Legs of ladder”

Phosphate &Sugar Backbone

DNA backbone

• Sugar• Phosphate

DNA Structure

• Rungs of the Ladder:–Various orders ofA, T, C, G

• Backbone:–Sugar and phosphates–Alternate

DNA Double Helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

 National DNA Day, April 25, 2009

• DNA SONG AND VIDEOhttp://www.terrificscience.org/general/dnavideo.jsp

What’s RNA?

• Ribonucleic Acid–Three types:–mRNA–tRNA–rRNA

Comparing DNA and RNA

• DNA• Double stranded• Sugar =

deoxyribose• Bases: A-T, C-G• Found only in

nucleus• Can repair itself

• RNA• Single stranded• Sugar = ribose• Bases: A-U, C-G• Found in and out of the nucleus • Cannot repair itself

RNA DNA

Pretty Similar

• Uracil• Thymine

DNA RNA

- Contains Thymine

- Contains deoxyribose sugar

- Double stranded molecule

- Found only in nucleus

- Single stranded molecule

- Contains uracil

- Contains ribose sugar

- Found in nucleus and cytoplasm

- Made of nucleotides

- Contain adenine, guanine and cytosine

Both

• Bozeman Biology DNA and RNA Part 1• Griffith, Avery, Hershey and Chase,

Watson and Crick, pro and eukaryotic chromos

• Bozeman Biology DNA and RNA part 2• DNA replication• Transformation• Protein synthesis

Relative Proportions (%) of Bases in DNA Organisms

A T G C• Human 30.9 29.4 19.9 19.8 • Chicken 28.8 29.2 20.5 21.5 • Grasshopper 29.3 29.3 20.5 20.7 • Sea Urchin 32.8 32.1 17.7 17.3 • Wheat 27.3 27.1 22.7 22.8 • Yeast 31.3 32.9 18.7 17.1 • E. coli 24.7 23.6 26.0 25.7

Question:

• If there is 30% Adenine, how much Cytosine is present?

• HINT: A –T and C - G

Answer:

• There would be 20% Cytosine.

Adenine (30%) = Thymine (30%)

Guanine (20%) = Cytosine (20%)

Total of 100%

Chargaff’s Rules

• the amount of (A)denine will always equal the amount of (T)hymine

• And• the amount of

(G)uanine will always equal the amount of (C)ytosine.

HOT!!!

Nitrogenous Bases

• Why does A bond only with T and C only with G?

• What do you notice?

Nitrogenous Bases

T and C are single-ring

Pyrimidines

A and G are double-ring

Purines

A single bonds with a

double

2 chains of nucleotides bind to form a DNA molecule

• Hydrogen bonds form between the nitrogenous bases to join the 2 chains together

• The sugar and phosphate group together is known as the sugar-phosphate backbone

ENZYMES FOR DNA REPLICATION

• Helicase = separates 2 DNA strands (breaks H bonds)

• Primase=RNA primers at INITIATION

REPLICATION ENZYMES

• Topoisomerase = unwinding DNA

• DNA Polymerase = Adding of DNA nucleotides ELONGATION (proofread and repair)

DNA REPLICATION ENZYMES

• LIGASE= Binds the Okazaki fragments

• Watch the enzymes in DNA Replication Animation

AT and C-G Base Pairing

• DNA Replication simple version) (link)• Media Showcase (cool animation link)• Detailed Replication Link

DNA STRUCTURE

• A-T• C-G• in tons of

combinations makes our genetic code

DNA Replication

•Hi!...Still Awake?

•DNA Replication Animation click here

What is the complementary base sequence on the other strand of the

DNA?

• T A A C G G G A T T

A T T G C C C T A A

The Race is On!

• To Determine the Structure of the DNA molecule.

DNA Geek

• Rosalind Franklin was an English chemist who was working in an X-ray crystallography lab in Paris, France in 1951.

FAMOUS PHOTO 51

(correct orientation of DNA)

Linus Pauling

• American biochemist suggested helix (spiral)shape

• Most famous for Vitamin C prevents colds

DNA Geek

• Linus Pauling was a Caltech chemist (USA), who in 1951 had discovered the alpha helical nature of protein structure.

I remember his books: Vitamin C and the Common Cold and Cancer and Vitamin C alsoThe Nature of the Chemical Bond and protested nuclear testing

DNA Geeks

• James Watson, a biologist from Indiana University, and Francis Crick, a physicist, were working at the Cavendish Lab in Cambridge, England Nobel Prize for structure of DNA

Francis Crick (1916-2004)Narrative - 8. Watson and Crick - Linus Pauling and the Race for DNA: A

Documentary History

• Born in England

• Worked at Cambridge

Crick’s first DNA sketch

Worked on DNA structure with Watson

James Watson (1928- )• American age 22• Ph.D. degree in Zoology in

1950 • Worked with Crick at the

King’s College on the structure of DNA

• At age 12 starred on QUIZ KIDS TV show

• Recently at Cold Spring Harbor, NY, head of HGP

Watson and CrickMet and worked at the Cavendish Laboratory

Watson and Crick’s Wire Model

DOUBLE HELIX

First put the nitrogenous bases on the outside

DNA GeekMaurice Wilkins (1916-2004)

• New Zealand Born British Scientist

• It was his idea to study DNA by X-ray crystallographic techniques

• Nobel Prize

DNA Base Pairs

• Adenine with Thymine• Guanine with Cytosine

X ray Diffraction

Franklin’s Suggestion

DNA Bases

Franklin corrects Watson and Crick

• Told them their first model was incorrect

• They had put the bases on the outside

The Scandal

• Watson used her pictures(Photo 51) to determine that DNA spirals into a double helix.

• Little did Rosalind Franklin know that her laboratory colleague, Maurice Wilkins, was in the next room revealing months of her work to her competitor!

Rosalind Franklin

• Died of ovarian cancer at age 38 and so could not share in the Nobel Prize

• Her work did lead the way to work on viruses

• She was not included in the publication that reported the structure of DNA and she died before the Nobel Prize was given to Watson and Crick.

Nobel Prize

• In 1962 James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize in medicine or physiology for their determination in 1953 of the structure of deoxyribonucleic acid (DNA).

Violation of the

Scientists' Code of Honor

• It is necessary for scientists to share information with one another, for if they did not, science and knowledge would not develop and grow. However, the tacit agreement among scientists who use or borrow one another's findings is that proper credit must be given to the author or originator of the work.

Beadle and Tatum’s Experiment• used X rays to cause mutations in

strains of the mold Neurospora (a bread mold)

• were able to create single gene mutations that incapacitated specific enzymes

Beadle and TatumThe One Gene/One Enzyme Hypothesis

Beadle and Tatum

EXPLAIN:

•“The secret of life is complementarity.”

Happy DNA DAY

The day commemorates the completion of the Human Genome Project in April 2003, and the discovery of DNA's double helix. DNA Song

NOVA | Ghost in Your Genes | PBS