DNA! DNA The Molecule of Life The molecule of life

Griffith Experiment conducted in 1928 Virulent (infectious) and avirulent (non- infectious) strains of bacteria Rough strain=avirulent Smooth strain=virulent

From this, Griffith discovered…Bacterial Transformation

Avery, MacLeod and McCarty (1944) What conclusions can be made from their results?

Hershey and Chase Alfred Hershey and Martha Chase - 1952 Studied bacteriophage; a virus that invades bacteria Labeled protein with radioactive sulfur Labeled DNA with radioactive phosphorus What can we conclude from their results?

Rosalind Franklin Rosalind Franklin was a female scientist working with DNA Performed x-ray crystallography to reveal structure of DNA in 1952 Her data was given away without her knowledge

Watson & Crick James Watson and Francis Crick used Franklin’s photographs to determine structure of DNA 1953-made model and published article about structure of DNA

DNA = Deoxyribonucleic Acid Holds genetic information of cells DNA kept in the nucleus Forms double helix

Connection to Macromolecules DNA is a nucleic acid The monomer of a nucleic acid is a nucleotide 3 parts of a nucleotide Nitrogenous Base 5-Carbon sugar Phosphate group Draw and label this in your notes!

Two Categories of Nitrogen Bases Each NUCLEOTIDE is the same, except for its nitrogen base A nitrogenous base can either be a PYRIMIDINE or a PURINE 1 Carbon Ring 2 Carbon Rings

Nitrogen Bases Adenine (purine) Thymine (pyrimidine) Guanine (purine) The 4 nitrogenous bases found in DNA are: Adenine (purine) Thymine (pyrimidine) Guanine (purine) Cytosine (pyrimidine)

What bases are purines? Pyrimidines?

Chargaff’s Discovery He found that the amount of adenine always equaled thymine and that the amount of guanine always equaled cytosine However the amount of A+T often did not equal the amount of C+G What do you think that he was able to conclude from this?

Complimentary base pairing Adenine always pairs with Thymine Cytosine always pairs with Guanine The 2 strands are joined by weak hydrogen bonds

2 chains of nucleotides bind to form a DNA molecule Hydrogen bonds form between nitrogenous bases to join the 2 chains together The sugar and phosphate group together is known as the sugar-phosphate backbone

What is the complementary base sequence on the other strand of the DNA? A T T G C C C T A A Template Strand Complementary Strand T A A C G G G A T T

DNA is anti-parallel Anti-parallel: the 2 strands run side- by-side in opposite directions AND are complimentary to each other

Test questions: If a section of DNA consisted of 30 nucleotides, and 10 of them were adenine nucleotides, how many thymine, guanine, and cytosine nucleotides are there? If the insulin gene consists of 40 base pairs, and 32 adenine nucleotides were present, how many guanine, cytosine, and thymine nucleotides are present?

Sugar-phosphate backbone Nitrogenous bases The classic picture of a DNA strand. You should now be able to recognize: Sugar-phosphate backbone Nitrogenous bases the 4 types Purines and Pyrimidines 2 chains of nucleotides Base-pairing rules