1. DNA = long molecule made up of repeating pieces
DNA makes genes Ch (p )
DNA = long molecule made up of repeating pieces
Like a chain made from the links
Each link is called a nucleotide ( a sugar, a phosphorous group, and one of four nitrogen-containing bases – see p. 186)
4 nitrogen bases:
2 called purines: Adenine (A) and Guanine (G)
2 called pyrimidines: Thymine (T) and Cytosine (C)

3. Sugar and phosphorous form the rails of the ladder
DNA Ch (p )
Double helix = structure of DNA, the twisted ladder or spiral staircase
Sugar and phosphorous form the rails of the ladder
The nitrogen bases form the steps of the ladder
Complementary
Base pairs = the nitrogen-bases always pair with their complement: A—T G—C
This is the genetic code, reading one side the other side matches

5. Helicase = enzyme that opens and “unzips” the double helix
DNA Ch (p )
Replication = copying DNA by reading one side of the ladder and making a complement
Helicase = enzyme that opens and “unzips” the double helix
DNA polymerase = enzyme that move along the chains and copy
Mutation = a mistake in copying
What do the names of enzymes end in?

10. DNA Ch (p )