What carries genetic information?

What carries genetic information?

Agenda for Tuesday May 3rd 1. Intro DNA notes2.Create DNA

Timeline of Identifying Genetic Material

1. Genetic Material Transforms Bacteria - Frederick Griffith, 1931

2. DNA is the hereditary material - Oswald Avery, Colin MacLeod, and Maclyn McCarty, 1944

3. The Genetic Material is DNA - Alfred D. Hershey and Martha Chase, 1952

4. Erwin Chargaff, 1940’s and early 50's5. M.H.F. Wilkins and Rosalind Franklin, early 50’s6. James Watson and Francis H.C. Crick, 1953

Discovery of DNAGriffith• 2 strains of bacteria

– Smooth (pneumonia)– Rough (no pneumonia)

• Conclusion– Disease was passed– One strain was

transformed into the other

Discovery of DNA

Avery• Isolated macromolecules from killed S cells

– DNA, protein, lipids

• Found that living R cells exposed to S strain DNA turned into S cells

• Conclusion– DNA released– R strain incorporated this DNA into its cells

Discovery of DNAHershey and Chase• Bacteriophages – virus that attacks bacteria

– DNA and protein– Viruses must inject DNA into living cell

• Labeled both parts of virus (DNA and protein)– Radioactive isotopes– DNA – labeled phosphorous– Proteins – labeled sulfur

• Conclusion– DNA provided info needed to produce new viruses

DNA - Deoxyribose nucleic acid• Store and transmit genetic

information

• Composed of smaller nucleotides

• DNA is an ideal genetic material– store information– able to replicate– undergo changes (mutate)

Structure of DNA

Nucleotides – 3 parts• Deoxyribose sugar • Phosphate group• Nitrogenous base

– A, T, C, G

Nitrogenous Bases• 4 Bases

– Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

• Purine – Double ring– A and G

• Pyrimidine – single ring– T and C

Chargaff’s Rule• Found amount of guanine equals amount of

cytosine– Amount of adenine nearly equals thyamine

• Chargaff’s rule: C=G A=T

Discovering Structure of DNA

X – Ray Diffraction• Maurice Wilkins and Rosalind Franklin• Photo 51• Indicated DNA was a double helix• http://www.pbs.org/wgbh/nova/photo51/

James Watson and Francis Crick Double Helix Model

• Used Franklin’s Photo and Chargaff’s dataFeatures of Model**Similar to ladder that is twisted**1. Sides formed by sugar-phosphate backbone2. rungs (or steps) formed by hydrogen bonding

between bases of nucleotides3. bases display complimentary base pairing --

purine always bond to a pyrimidine – A always bonds with T and G always bonds with C

DNA is Complementary

• Complementary: bases on one strand match up with the bases on the other strand – (A-T and G-C)

Example: Strand 1- ATG GGC CTA Strand 2- TAC CCG GAT

Orientation of DNA• The nucleotides form a chain

• The phosphate end of the chain is referred to as the 5' end. The opposite end is the 3' end.

• Q: Since DNA is complementary, what end matches with the 5’ end?

Final Thoughts:DNA

• Similar to a ladder– Rails (outside of ladder)

are deoxyribose and phosphate

– Base pairs are rungs of ladder

– Twisted

Remember

DNA is like an Oreo

Phophates + sugars = cookiesBases = cream filling

Chromosome Structure

• Prokaryotes – DNA is in the shape of a ring

• Eukaryotic – chromosomes– 51 – 245 million base pairs– 5 centimeters– Coils tightly around histones and forms nucleosome– Nucleosome group together and form chromatin

fibers– Chromatin fibers form chromosomes

Chromosome Structure

Histones

Nucleosomes

Chromatin Fibers

•DNA wraps around histones•8 histones combine to form nucleosome

Person/People Accomplishment and Description

Year

Remember!!

• 2 strands allow bases to pair– A binds T with 2 H bonds– C binds G with 3 H bonds

Phosphates + sugars on the outside

Bases on the inside (Bases fit like puzzle pieces)

Info on Bases• Purine – double ring base

– Guanine, Adenine

• Pyrimidine – single ring base– Cytosine, Thymine

What is a nucleotide made of (3 parts)?

Agenda for Wednesday May 4th 1.Create DNA

What shape is DNA? How was this discovered?

Agenda for Thursday May 5th 1.Finish Making DNA2.DNA Extraction lab