- DNA as genetic material - Structure of DNA - DNA replication Sections 8.1, 8.2, and 8.3

What is this stuff?

Deoxyribonucleic Acid Consists of 4 bases DNA!!! Deoxyribonucleic Acid Consists of 4 bases Adenine Thymine Guanine Cytosine

Did experiments with 2 different types of pneumonia Frederick Griffith Did experiments with 2 different types of pneumonia Smooth vs. rough Smooth covered in with sugars Rough does not have this covering

His experiment

Called the mystery material “transforming principle” Why did this happen? Some sort of material must have transferred between the live R and the heat killed S Did not know it was DNA just yet Called the mystery material “transforming principle”

Combined lived R bacteria with extract from S bacteria Oswald Avery Worked on extending Griffiths work 10 years!!! Combined lived R bacteria with extract from S bacteria Were able to directly observe the change of R bacteria into S

Avery’s experiments Qualitative tests Chemical analysis Enzyme tests Chemical tests showed there was actually NO proteins present. Only DNA Chemical analysis These show the amounts or proportions of elements found in DNA. Proteins hardly contain phosphorus Enzyme tests Enzymes known to break down proteins and RNA did nothing to stop the transformation. Only enzymes that broke down DNA stopped the process

Confirmed DNA as genetic material in 1952 Hershey and Chase Confirmed DNA as genetic material in 1952 Studied viruses that infected bacteria Bacteriophages Take over a bacterial cell to make more bacteriophages Very simple things A small amount of DNA covered by a protein coat

Bacteriophages!!!

How do they work?

Proteins WERE NOT passed to the bacteria from the bacteriophages Their experiments Experiment 1 Tagged radioactive sulfur atoms on phage’s protein molecules Let phages infect bacteria Studied bacteria after they were infected Found very little radioactivity present in bacteria Proteins WERE NOT passed to the bacteria from the bacteriophages

Their experiments Experiment 2 Tagged phosphorus molecules in the phage’s DNA with radioactivity Let phages infect bacteria Studied bacteria after they were infected Found A LOT of radioactivity within the bacteria DNA was passed to bacteria. More phages are made within the bacteria. Increased phages = increased radioactive tags

2 parts to the “backbone” 1 phosphate group Ring-ring shaped sugar DNA structure Consists of 4 bases or nucleotides 2 parts to the “backbone” 1 phosphate group Ring-ring shaped sugar deoxyribose

Adenine always pairs with Thymine Base pairing rules Adenine always pairs with Thymine Double ring with double ring Guanine always pairs with Cytosine Single ring with single ring A=T and C=G Chargaff’s rule

Base pairing practice GTA CTTGAC GATTACA TTGGACCGGAT

Got credit for the shape of DNA Watson and Crick Got credit for the shape of DNA Used an image they were not supposed to have Stolen from Rosalind Franklin They waited until she died before submitting their results to be published Ended up winning the Nobel Prize She got no posthumous credit for “their” work

Split into 2 groups