Biology 2.1

AQA BIO2 Chapter 1

• Made up of a pentose sugar called deoxyribose.
• Phosphate Group has a negative charge so DNA can be seperated.
• The base of a nucleotide can be any one of 4 
  • Adenine
  • Guanine
  • Cytosine
  • Thymine
• Adenine and Guanine are Purines.
• Cytosine and Thymine are Pyrimidines

Single nucleotides undergo a condensation reaction to form a phosphodiester bond between the phosphate group of one nucleotiode and the deoxyribose sugar of another nucleotide, when this occurs between several nucleotides a polynucleotide strand is formed

A Sugar Phosphate Backbone is formed between the pentose sugars and the phosphate group.

Base Pairing

bases only pair if they are complementary, hydrogen bond form between complementary bases

A=T require 2 hydrogen bonds.

G≡C requires 3 hydrogen bonds.

Base pairs involve 1 purine base and 1 pyrimidine base.

DNA

comprised of 2 polynucleotide strands that run anti-parralel to each other, each strand has bases that are complementary to the other strand

hydrogen bonds hold the two strands together.

5' end is when the…