Today’s Objectives: DNA Structure Notes DNA Song Finish Race to DNA Happy Friday! Today’s Objectives: DNA Structure Notes DNA Song Finish Race to DNA Practice Page

DNA Structure

DNA Scientists Watson and Crick (1950s) Credited with discovering DNA Rosalind Franklin (1950s) Helped discover the structure of DNA Wilkins (1950s) Took X-ray pictures of DNA Chargoff (1940s) Determined base pairing rules

DNA Structure DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. A molecule of DNA is made up of millions of tiny subunits called Nucleotides. Each nucleotide consists of: phosphate group 5-carbon sugar (DNA = deoxyribose) nitrogenous base

Nucleotide (Draw on the back of your paper!) Nitrogenous Base 5-carbon Phosphate Nitrogenous Base 5-carbon Sugar (Draw on the back of your paper!)

Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

Nucleotides: Nitrogen Bases Adenine T Thymine C Cytosine G Guanine

Pyrimidines have a “y” in their name! Nitrogen Bases Two Types: Purines: Double ring structure Adenine Guanine Pyrimidines: Single ring structure (like a pie) Thymine Cytosine Pyrimidines have a “y” in their name!

Scientist responsible for complimentary base pair rules: Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Scientist responsible for complimentary base pair rules: Erwin Chargaff base pair base pair

C+G = Cows and Goats OR CoverGirl How can we remember?? A+T = At C+G = Cows and Goats OR CoverGirl

DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

A C T G G A T C

Bonds in DNA Hydrogen Bonds: hold nitrogen bases together (in the middle) Covalent Bonds: hold sugar from one nucleotide to phosphate of a neighboring nucleotide (on the edges)

Bonds in DNA Hydrogen Bonds Covalent Bonds