Bio INTRO TO DNA FUNCTION/ROLES

DNA

• Deoxyribonucleic acid is a coiled double helix carrying hereditary information of the cell

• DNA is a polymer – made from small repeating monomer units.

• The monomer of DNA is called a Nucleotide

1. Sugar - Deoxyribose

2. Phosphate Group

3. Nitrogen Base

Role

• Storing Information

• Copying Information

• Transmitting Information

Gene

Instructions to build a protein

DNA must be copied why

So cells can grow, repair, and reproduce

Mistakes and Mutated copies of genes lead to

greater diversity and drives evolution

Nucleotide

• The bonding of these three parts is accomplished by dehydration synthesis (water removal).

• The bonds formed are strong covalent bonds keeping the nucleotide intact.

Nitrogen Bases

Adenine and Guanine

• Called Purines

• Notice: Double Ringed Structures

Cytosine and Thymine

• Called Pyrimidines

• Notice: Single Ringed Structures

Adenine always pairs with Thymine

Cytosine always pairs with Guanine

This is known as Complementary Base Pairing

**DNA is**

**antiparallel. Its two strands run in opposite directions.**

**Hydrogen Bonding**

• The nitrogen bases are linked by very weak hydrogen bonds:

• A double hydrogen exists between adenine and thymine

• A triple hydrogen bond exists between guanine and cytosine

• Bonds are very weak here because during DNA replication, they must be broken. It requires less energy from the cell to break these bonds.