The Structure of:

 By the end of the day, you should:  Know what DNA stands for  Understand the shape of DNA and be able to label all parts  Know the pairs of nucleotides  Know how DNA is used

 DNA is the molecule that carries genetic information  So what does that really mean?

 DNA stands for deoxyribonucleic acid  We’ll come back to this one…

 The shape of the DNA molecule is called a double helix  Think of DNA’s shape as a ladder that has been twisted Straight Twisted Ladder

 It’s nice to think of DNA looking nice and simple like this:

 But, it really looks more like this: Let’s break it down…

 Each side of the ladder is called a sugar-phosphate backbone this part

 The sugar-phosphate backbone…up close  Consists of: ▪ Phosphate group ▪ Deoxyribose sugar group

 The rungs of the latter are made up of nitrogenous bases  Bonded to the sugar group  There are 4 different kinds of bases in DNA…

Purines Pyrimidines

 A deoxyribose sugar group and a phosphate group and a nitrogenous base make up a nucleotide P P P P Adenine Guanine Cytosine Thymine

 The deoxyribose sugar group of one nucleotide bonds to the phosphate group of another nucleotide to form the sugar- phosphate backbone  The nitrogenous bases of one sugar-phosphate backbone bond to the nitrogenous bases of the other sugar-phosphate backbone to make base pairs  A only bonds with T  G only bonds with C

 Quick Practice:  If you had a strand of DNA where one side had this sequence of bases: ATAGGCAT  What would the other side’s sequence be???

P A P A P G P C P C P G P T P T

 Now that you know about the structure of DNA, let’s revisit its function…

 Short version: DNA stores genetic information  Long version: The sequence (order) of bases on the strand of DNA is a code for a blueprint of hundreds of thousands of different proteins that, when made, make up living things