A Quick Review! What determines a proteins function? Its shape. What if you change its shape (by heating it for example? It stops working. What determines the shape of a protein? Its 1o structure or sequence of amino acids. What happens if you change an amino acid in the sequence of a particular protein? It will fold slightly differently and not work properly (or at all!). Why? The side groups of the amino acids form bonds with each other which results in 2o and 3o structure.

Our Guiding Question WHAT DETERMINES THE ORDER OF AMINO ACIDS IN A PROTEIN???

DNA What is DNA? http://www.youtube.com/watch?v=zwibgNGe4aY (Deoxyribonucleic Acid) What is DNA? http://www.youtube.com/watch?v=zwibgNGe4aY

Questions about DNA? What does DNA look like? How is DNA made? How do we know DNA has the instructions to make proteins? How does DNA instruct the cell to make proteins?

DNA is universal to life All living organisms have DNA Bacteria, fungi, plants, animals…and even many viruses The function of DNA is to store information for an organism’s characteristics

The nucleus stores DNA in eukaryotic cells Elodea leaf cell human cheek cell mitochondria chloroplasts vacuole nucleus (DNA here) (DNA here)

Prokaryote cells do not have a nucleus but DO have DNA E. coli bacteria cell DNA

In the cell, DNA forms structures called chromosomes A eukaryotic chromosome is typically a very long, single chain of DNA

In the cell, DNA forms structures called chromosomes A prokaryotic chromosome is typically a circular chain of DNA Prokaryotic cells also often have smaller circles of DNA called plasmids E. coli bacteria cell Chromosome DNA Plasmid DNA

What does DNA look like? We will begin our investigation into DNA by looking at its structure.

DNA is a double helix The shape of a DNA molecule is like a twisted ladder or spiral staircase http://biomodel.uah.es/en/model4/dna/dnapairs.htm

DNA is a polymer made of monomers called nucleotides A nucleotide has 3 parts: a phosphate, a sugar, and a base. PHOSPHATE http://biomodel.uah.es/en/model4/dna/dnapairs.htm BASE SUGAR

There are 4 DNA nucleotides They are the same except for their bases Adenine Thymine Cytosine Guanine

Making a DNA molecule One strand of a DNA molecule is formed by linking together the sugars and phosphates of nucleotides.

Hydrogen bonds The two strands (halves) of a DNA molecule are connected by hydrogen bonds between the bases of nucleotides. http://biomodel.uah.es/en/model4/dna/dnacode.htm Click on the “Replicate DNA” button on the bottom of the jmol model page to make clear the base-pairing relationships Hydrogen bonds

Complementary base pairing In DNA molecules… Adenine only bonds to thymine. Cytosine only bonds to guanine. A—T G—C AT and GC buttons not working on jmol model

DNA Structure Your goals: Build the 4 different Nucleotides by your self Take 2 of your Nucleotides (whichever you would like) and add it to the class DNA molecule We will use the other Nucleotides in the second part of class Students can work in pairs to make the 4 nucleotides to cut down on materials