The Structure of D.N.A.

Brain Tap What do we know about DNA?

D.N.A Deoxyribose Nucleic Acid Found in the nucleus of cells Ultimate function is to store and transmit genetic information that tells cells which proteins to make, and when to make them

Structure An Organic compound, made up of repeating subunits called NUCLEOTIDES Each DNA molecule consists of two long chains of nucleotides Each DNA Nucleotide has 3 parts Deoxyribose- 5 carbon sugar molecule Phosphate Group- phosphorous (P) atom, surrounded by Oxygen (O) Nitrogen-containing base- Containing Nitrogen (N) atom 4 different types of Nitrogen-containing bases

D.N.A Nucleotide

Nitrogenous bases Four Nitrogen-Containing bases found in DNA nucleotides: Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

Separated into two groups Purines: Adenine and Guanine Characterized by two rings of Carbon and Nitrogen Pyrimididines: Thymine and Cytosine Characterized by one ring of Carbon and Nitrogen

The Double Helix Watson and Crick (1950s)- suggested the “double helix” model for DNA, providing explanation for how DNA can be made and how genetic info may be stored in cell Alternating Deoxyribose sugar molecules and phosphate group molecules form the backbone of to which nitrogenous bases attach (one strand of DNA)

Double Helix Nitrogen bases, face towards centre of helix Allows one strand of DNA to face the bases on another strand Form Hydrogen Bonds between N-bases of other DNA strand Base pairing will be uniform in length as a 2-ring purine will always match with a 1-ring pyrimidine

Complementary Base Pairing Notice in all the diagrams Guanine pairs with Cytosine, Thymine pairs with Adenine These pairs of bases are Complementary Base pairs General Rule: these base pairs will ALWAYS match up with one another (A-T, C-G) C-G Form 3 Hydrogen Bonds, A-T  For 2 Hydrogen Bonds (Fig 10.3)

Delicious D.N.A. DNA has made you, now it is your turn to make DNA! Please partner up, and follow along with your licorice lab manual!

Next Class Learn How D.N.A. makes copies of its self! DNAs single cousin, RNA Transcription