Happy Friday Todays Objectives DNA Structure Notes DNA

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DNA Structure

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

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: 1. phosphate group 2. 5 -carbon sugar (DNA = deoxyribose) 3. nitrogenous base

Nucleotide Phosphate Nitrogenous Base 5 -carbon Sugar (Draw on the back of

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 A Adenine C Cytosine T Thymine G Guanine

Nitrogen Bases Two Types: 1. Purines: Double ring structure 1. Adenine 2. Guanine 2. Pyrimidines: Single ring structure (like a pie) 1. Thymine Pyrimidines have 2. Cytosine a “y” in their name!

Nucleotides �Each base will only bond with one other specific base. �Adenine (A) �Thymine (T) �Cytosine (C) �Guanine (G) base pair Scientist responsi ble for complim entary base pair

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

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

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 Covalent Bonds Hydrogen Bonds