Deoxyribo- nucleic Acid is made up of nucleotides.

DNA

DNA Structure

Deoxyribo-nucleic Acid is made up of nucleotides

Nucleotides have 3 parts› Deoxyribose (sugar)

› Phosphate group› Nitrogenous base

Deoxyribose and Phosphate are in all nucleotides, but there are 4 different nitrogenous bases› Adenine› Guanine› Cytosine› Thymine

All nitrogenous bases contain rings

Adenine and Guanine contain 2 rings and are called Purines

Cytosine and Thymine contain 1 ring and are called Pyrimidines

Remember the phrase:› Pure As Gold

DNA History In 1953, Scientists

Watson and Crick made a model of DNA as a double helix – the spiral staircase shape.

When untwisted looks like a ladder

The sides of the ladder are the backbone and alternate with deoxyribose and phosphate

The bases bond the two strands in the middle

A purine always bonds with a pyrimidine so the length is the same

They are bonded together by hydrogen bonds

Complementary Base Pairing

Cytosine always bonds with Guanine› Hint: (C and G

are letters that look alike)

Adenine always bonds with Thyamine› Hint: (A and T

are letters made of straight lines)

What is the complementary base sequence of this strand of DNA?

The order and sequence of these bases is what makes each of us different from one another and different from other species